The P3 event-related potential (ERP) component was recorded from 7- to 18-year-old children of alcoholics (COAs, n = 50) and age- and sex-matched control children (n = 50) using a visual oddball paradigm, involving nontarget (76%), target (12%), and novel (12%) stimuli. Topographic maps of P3 and associated scalp current density were obtained to supplement a topographic profile analysis. COAs manifested a smaller amplitude P3 to target stimuli over the centroparietal, parietal, and occipital scalp locations than controls. Also, COAs exhibited a smaller amplitude P3 to novel stimuli over the occipital scalp than controls. There were no significant differences between COAs and controls in the P3 scalp topography, indicating that differences in intracranial source strength rather than in source configuration were responsible for the between-group amplitude differences. Also, no significant group differences were observed in the P3 peak latency or in behavioral performance. These results support the notion that the visual P3 may provide a vulnerability marker of alcoholism.