Changes in saccadic eye movements before and after up to 10 mg oral diazepam were measured electrooculographically in diazepam-naive humans. Diazepam produced dose-dependent increases in saccade duration and decreases in maximum saccade velocity over a 2--36 degrees range of saccade amplitudes. The magnitude of drug-induced changes in saccade performance was proportional to the size of saccadic movement after 10 mg diazepam. Accuracy of saccade, latency to onset of saccade, latency to time of maximum velocity of saccade, and interval between the end of the initial saccade and the start of any corrective saccade were unaffected by the drug. Diazepam-induced changes in saccades were compared to saccades seen in patients with olivopontocerebellar atrophy reported in the literature, and were contrasted with saccade changes caused by opiates as reported previously. The possible participation of cerebellum in changes in saccadic function after diazepam was discussed.