Sixty-three medical residents were tested on a battery of computer-based, self-administered neurobehavioral tests before and after a 36-hour in-hospital call plus postcall day to assess the central nervous system effects of the call experience and its accompanying sleep deprivation. Statistically significant decreases in performance were found postcall on tests of sustained visual attention (P < 0.0001), speed and coding ability (P < 0.0001) and short-term recall (P < 0.0001). Hand-eye coordination improved (P < 0.02).