Accuracy in manual manipulation in a simulated microsurgical environment has been studied. Three vitreoretinal microsurgeons completed a series of static and dynamic tasks. Results for overall rms position error, overall maximum position error, and estimated physiological tremor amplitude were calculated. The rms amplitude of the error vector in three dimensions averaged 166 mum in a stationary pointing task, and 2009-4506 mum in the dynamic tasks. The maximum error vector magnitude during the stationary task averaged 408 mum during the stationary tests, and 3531-6788 mum in the dynamic tasks. The rms amplitude of tremor during the stationary task averaged 76-101 mum in the three spatial coordinates, with an average vector magnitude of 156 mum rms.