Eye movements were recorded with the search coil system in two patients to determine whether lesions of the pontine nuclei selectively impair vergence to ramp targets (slow vergence) or step targets (fast vergence). Whereas conjugate saccades were not different from healthy control subjects, conjugate smooth pursuit eye movements had a reduced gain in horizontal and vertical directions. Slow convergence and divergence were impaired, whereas fast vergence did not differ from that of control subjects. Pontine nuclei appear to be involved in the slow vergence control.