The present study examined event-related potentials (ERPs) elicited by a visual discrimination task in a community sample of adult males with a lifetime diagnosis of alcohol dependence. Study participants were subtyped by the presence of additional comorbid disorders (antisocial personality, depression, and drug abuse or dependence). In all groups of alcohol-dependent subjects, even those without any additional comorbid disorders, P3 amplitude differed from that of a comparison group. Alcohol-dependent subjects with a diagnosis of illicit drug abuse or dependence, especially if they had antisocial personality as well, had the smallest amplitude responses. The amplitude profile of the P3 across the parietal electrodes used as active sites was flattened among alcoholic subjects, with P3 amplitude disproportionately reduced at the midline. Among alcoholic subjects with a lifetime diagnosis of depression, the flattened amplitude profile was due to elevated mean amplitude of the P3 at lateral leads, especially P4, relative to the comparison group. Alterations in ERP responses appear to be a general characteristic of alcoholism in men, although the presence of other comorbid disorders, particularly drug abuse or dependence together with antisocial personality, results in the greatest reductions in P3 amplitude.