I searched in the ode files, and found dAASSERT \ode-0.7\include\ode\common.h line 93: #define dAASSERT(a) dUASSERT(a,"Bad argument(s)") and dUASSERT is: #define dUASSERT(a,msg) if (!(a)) dDebug (d_ERR_UASSERT, msg " (%s:%d)", __FILE__,__LINE__); for other words, just try to search in the ode files bye chris