Studies evaluating the effects of diazepam (Valium) on psychomotor and cognitive functions are reviewed an integrated. The importance of the full and clear documentation of such drug effects lies in the wide usage of diazepam today for a variety of medical, psychiatric, and dental purposes. The various tasks used to assess drug effects were classified into six major groups based on apparent similarity of functions tapped. These groupings are: reflex speed; critical flicker fusion threshold; attention and vigilance; decision making; learning and memory; psychomotor performance. In all functions except simple reflexive responding; some indications of impaired performances were reported, the results being most definitive for the critical flicker fusion where even small doses lowered the threshold and for a slower performance on letter cancellation tasks. There appeared to be some interaction between diazepam and alcohol although the nature of this interaction is still unclear. Because of the extensive use of both of these drugs and the possibility of a synergistic or a potentiation effect, it is important that this area receive further study. It was suggested that future studies either control for or analyze the data to assess the possible interactive effects of diazepam with subject variables such as sex, personality type, and for population characteristics. These variables have been shown to affect responses in other studies and hence could also interact with cognitive and psychomotor performance. It was noted that most of the studies reviewed used normal, healthy, male volunteer subjects and may not be comparable to the clinical populations for whom the drug is typically prescribed.