ncurses does not support the scrollwheel well, but this is a step in that direction.

htop.c

 /*
 htop - htop.c
-(C) 2004-2010 Hisham H. Muhammad
+(C) 2004-2011 Hisham H. Muhammad
 Released under the GNU GPL, see the COPYING file
 in the source distribution for its full text.
 */
@@ -37,7 +37,7 @@ in the source distribution for its full text.
 
 #define INCSEARCH_MAX 40
 
-#define COPYRIGHT "(C) 2004-2010 Hisham Muhammad"
+#define COPYRIGHT "(C) 2004-2011 Hisham Muhammad"
 
 static void printVersionFlag() {
    fputs("htop " VERSION " - " COPYRIGHT "\n"
@@ -496,6 +496,7 @@ int main(int argc, char** argv) {
          MEVENT mevent;
          int ok = getmouse(&mevent);
          if (ok == OK) {
+            if (mevent.bstate & BUTTON1_CLICKED) {
                if (mevent.y == panel->y) {
                   int x = panel->scrollH + mevent.x + 1;
                   ProcessField field = ProcessList_keyAt(pl, x);
@@ -519,7 +520,13 @@ int main(int argc, char** argv) {
                   else bar = defaultBar;
                   ch = FunctionBar_synthesizeEvent(bar, mevent.x);
                }
-
+            } else if (mevent.bstate & BUTTON4_CLICKED) {
+               ch = KEY_UP;
+            #if NCURSES_MOUSE_VERSION > 1
+            } else if (mevent.bstate & BUTTON5_CLICKED) {
+               ch = KEY_DOWN;
+            #endif
+            }
          }
       }