ERPs were recorded during a simple color discrimination and a more difficult visual continuous performance task (CPT) from three father-son (n = 15) pair groups: recovering alcoholics with a family history of alcoholism and their sons (A+), nonalcoholics with a family history of alcoholism and their sons (NA+), and nonalcoholics with no family history of alcoholism and their sons (NA-). The sons, aged 8 to 12, had not begun drinking or using other drugs. Groups were matched on age, education and socioeconomic status. There were two principal findings. Compared to nonalcoholic groups, both A+ sons and fathers exhibited increased latency and decreased amplitude of P3 for the difficult task, but not for the easy task. This result helps to explain previous inconsistencies in the literature, and strengthens the suggestion that one indication of a vulnerability to develop alcoholism is an abnormal P3, when elicited by an appropriate task. Additionally, A+ fathers had more negative amplitudes for a late slow wave in both tasks, suggesting electrophysiological consequences of long-term alcohol abuse.