The present study evaluated pattern shift visual evoked potential (VEP) amplitudes and latencies in four groups of adult subjects, characterized by the presence/absence of a recent history of alcohol dependence factorially crossed with the presence/absence of a recent history of cocaine dependence. All of the subjects were healthy and uncomplicated by histories of serious head injury, seizures (including drug-related seizures), and major medical, neurological, or psychiatric disorders. The subjects comprising the three patient groups were evaluated after 1 - 5 months of verified abstinence. Analyses of VEPs evoked by checkerboard reversal indicated a main effect of previous cocaine dependence on P100 latency. No main effect of previous alcohol dependence and no alcohol by cocaine dependence interaction were detected. The increased P100 latencies detected in abstinent, cocaine-dependent subjects are most likely related to cerebrovascular and neurological effects of chronic cocaine use.