diff --git a/http_modifier.go b/http_modifier.go
index b6f994c..3aa0476 100644
--- a/http_modifier.go
+++ b/http_modifier.go
@@ -15,6 +15,7 @@ func NewHTTPModifier(config *HTTPModifierConfig) *HTTPModifier {
 		len(config.urlRewrite) == 0 &&
 		len(config.headerFilters) == 0 &&
 		len(config.headerHashFilters) == 0 &&
+		len(config.paramHashFilters) == 0 &&
 		len(config.headers) == 0 &&
 		len(config.methods) == 0 {
 		return nil
@@ -60,15 +61,28 @@ func (m *HTTPModifier) Rewrite(payload []byte) (response []byte) {
 		for _, f := range m.config.headerHashFilters {
 			value, s, _, _ := proto.Header(payload, f.name)
 
-			if s == -1 {
-				return
+			if s != -1 {
+				hasher := fnv.New32a()
+				hasher.Write(value)
+
+				if (hasher.Sum32() % 100) >= f.percent {
+					return
+				}
 			}
+		}
+	}
 
-			hasher := fnv.New32a()
-			hasher.Write(value)
+	if len(m.config.paramHashFilters) > 0 {
+		for _, f := range m.config.paramHashFilters {
+			value, s, _ := proto.PathParam(payload, f.name)
 
-			if (hasher.Sum32() % 100) >= f.percent {
-				return
+			if s != -1 {
+				hasher := fnv.New32a()
+				hasher.Write(value)
+
+				if (hasher.Sum32() % 100) >= f.percent {
+					return
+				}
 			}
 		}
 	}
diff --git a/http_modifier_settings.go b/http_modifier_settings.go
index 5ea8601..391854a 100644
--- a/http_modifier_settings.go
+++ b/http_modifier_settings.go
@@ -14,7 +14,8 @@ type HTTPModifierConfig struct {
     urlRegexp         HTTPUrlRegexp
     urlRewrite        UrlRewriteMap
     headerFilters     HTTPHeaderFilters
-    headerHashFilters HTTPHeaderHashFilters
+    headerHashFilters HTTPHashFilters
+    paramHashFilters  HTTPHashFilters
 
     headers HTTPHeaders
     methods HTTPMethods
@@ -50,20 +51,20 @@ func (h *HTTPHeaderFilters) Set(value string) error {
 }
 
 //
-// Handling of --http-allow-header-hash options
+// Handling of --http-allow-header-hash and --http-allow-param-hash options
 //
-type headerHashFilter struct {
+type hashFilter struct {
     name    []byte
     percent uint32
 }
 
-type HTTPHeaderHashFilters []headerHashFilter
+type HTTPHashFilters []hashFilter
 
-func (h *HTTPHeaderHashFilters) String() string {
+func (h *HTTPHashFilters) String() string {
     return fmt.Sprint(*h)
 }
 
-func (h *HTTPHeaderHashFilters) Set(value string) error {
+func (h *HTTPHashFilters) Set(value string) error {
     valArr := strings.SplitN(value, ":", 2)
     if len(valArr) < 2 {
         return errors.New("need both header and value, colon-delimited (ex. user_id:1/2).")
@@ -78,7 +79,7 @@ func (h *HTTPHeaderHashFilters) Set(value string) error {
     num, _ = strconv.ParseUint(fracArr[0], 10, 64)
     den, _ = strconv.ParseUint(fracArr[1], 10, 64)
 
-    var f headerHashFilter
+    var f hashFilter
     f.name = []byte(valArr[0])
     f.percent = uint32((float64(num) / float64(den)) * 100)
     *h = append(*h, f)
diff --git a/http_modifier_settings_test.go b/http_modifier_settings_test.go
index badf30e..0b1701d 100644
--- a/http_modifier_settings_test.go
+++ b/http_modifier_settings_test.go
@@ -24,8 +24,8 @@ func TestHTTPHeaderFilters(t *testing.T) {
     }
 }
 
-func TestHTTPHeaderHashFilters(t *testing.T) {
-    filters := HTTPHeaderHashFilters{}
+func TestHTTPHashFilters(t *testing.T) {
+    filters := HTTPHashFilters{}
 
     err := filters.Set("Header1:1/2")
     if err != nil {
diff --git a/http_modifier_test.go b/http_modifier_test.go
index 4689aca..80a3bb3 100644
--- a/http_modifier_test.go
+++ b/http_modifier_test.go
@@ -69,7 +69,7 @@ func TestHTTPModifierURLRewrite(t *testing.T) {
 }
 
 func TestHTTPModifierHeaderHashFilters(t *testing.T) {
-	filters := HTTPHeaderHashFilters{}
+	filters := HTTPHashFilters{}
 	filters.Set("Header2:1/2")
 
 	modifier := NewHTTPModifier(&HTTPModifierConfig{
@@ -80,8 +80,8 @@ func TestHTTPModifierHeaderHashFilters(t *testing.T) {
 		return []byte("POST / HTTP/1.1\r\n" + string(header) + "Content-Length: 7\r\nHost: www.w3.org\r\n\r\na=1&b=2")
 	}
 
-	if p := modifier.Rewrite(payload([]byte(""))); len(p) > 0 {
-		t.Error("Request should not pass filters, Header2 does not exist")
+	if p := modifier.Rewrite(payload([]byte(""))); len(p) == 0 {
+		t.Error("Request should pass filters if Header does not exist")
 	}
 
 	if p := modifier.Rewrite(payload([]byte("Header2: 3\r\n"))); len(p) > 0 {
@@ -93,6 +93,32 @@ func TestHTTPModifierHeaderHashFilters(t *testing.T) {
 	}
 }
 
+
+func TestHTTPModifierParamHashFilters(t *testing.T) {
+	filters := HTTPHashFilters{}
+	filters.Set("user_id:1/2")
+
+	modifier := NewHTTPModifier(&HTTPModifierConfig{
+		paramHashFilters: filters,
+	})
+
+	payload := func(value []byte) []byte {
+		return []byte("POST /" + string(value) + " HTTP/1.1\r\nContent-Length: 7\r\nHost: www.w3.org\r\n\r\na=1&b=2")
+	}
+
+	if p := modifier.Rewrite(payload([]byte(""))); len(p) == 0 {
+		t.Error("Request should pass filters if param does not exist")
+	}
+
+	if p := modifier.Rewrite(payload([]byte("?user_id=3"))); len(p) > 0 {
+		t.Error("Request should not pass filters", string(p))
+	}
+
+	if p := modifier.Rewrite(payload([]byte("?user_id=1"))); len(p) == 0 {
+		t.Error("Request should pass filters")
+	}
+}
+
 func TestHTTPModifierHeaders(t *testing.T) {
 	headers := HTTPHeaders{}
 	headers.Set("Header1:1")
diff --git a/proto/proto.go b/proto/proto.go
index 330115b..9b0e5cf 100644
--- a/proto/proto.go
+++ b/proto/proto.go
@@ -86,6 +86,24 @@ func SetPath(payload, path []byte) []byte {
     return byteutils.Replace(payload, start, start+end, path)
 }
 
+func PathParam(payload, name []byte) (value []byte, valueStart, valueEnd int) {
+    path := Path(payload)
+
+    if paramStart := bytes.Index(path, append(name, '=')); paramStart != -1 {
+        valueStart := paramStart + len(name) + 1
+        paramEnd := bytes.IndexByte(path[valueStart:], '&')
+        if paramEnd == -1 { // It is final param
+            paramEnd = len(path)
+        } else {
+            paramEnd += valueStart
+        }
+
+        return path[valueStart:paramEnd], valueStart, paramEnd
+    } else {
+        return []byte(""), -1, -1
+    }
+}
+
 func SetHost(payload, url, host []byte) []byte {
     // If this is HTTP 1.0 traffic or proxy traffic it may include host right into path variable, so instead of setting Host header we rewrite Path
     // Fix for https://github.com/buger/gor/issues/156
diff --git a/proto/proto_test.go b/proto/proto_test.go
index 3ada427..12227e2 100644
--- a/proto/proto_test.go
+++ b/proto/proto_test.go
@@ -89,6 +89,21 @@ func TestSetPath(t *testing.T) {
     }
 }
 
+func TestPathParam(t *testing.T) {
+    var payload []byte
+
+    payload = []byte("POST /post?param=test&user_id=1 HTTP/1.1\r\nContent-Length: 7\r\nHost: www.w3.org\r\n\r\na=1&b=2")
+
+    if val, _, _ := PathParam(payload, []byte("param")); !bytes.Equal(val, []byte("test")) {
+        t.Error("Should detect attribute", string(val))
+    }
+
+    if val, _, _ := PathParam(payload, []byte("user_id")); !bytes.Equal(val, []byte("1")) {
+        t.Error("Should detect attribute", string(val))
+    }
+}
+
+
 func TestSetHostHTTP10(t *testing.T) {
     var payload, payload_after []byte
 
diff --git a/settings.go b/settings.go
index 58b8400..aa9cb6d 100644
--- a/settings.go
+++ b/settings.go
@@ -110,6 +110,8 @@ func init() {
 
 	flag.Var(&Settings.modifierConfig.headerHashFilters, "http-allow-header-hash", "Takes a fraction of requests, consistently taking or rejecting a request based on the FNV32-1A hash of a specific header:\n\t gor --input-raw :8080 --output-http staging.com --http-allow-header-hash user-id:1/4")
 	flag.Var(&Settings.modifierConfig.headerHashFilters, "output-http-header-hash-filter", "WARNING: `output-http-header-hash-filter` DEPRECATED, use `--http-allow-header-hash` instead")
+
+	flag.Var(&Settings.modifierConfig.paramHashFilters, "http-allow-param-hash", "Takes a fraction of requests, consistently taking or rejecting a request based on the FNV32-1A hash of a specific GET param:\n\t gor --input-raw :8080 --output-http staging.com --http-allow-param-hash user_id:1/4")
 }
 
 func Debug(args ...interface{}) {