Subtyping alcoholics may provide a more accurate guide as to the course and character of the disease. Classifications of different ages of onset of problem drinking have so far resulted in categorical inconsistencies. In the past, hospital-based alcoholics have over-represented those most severely ill, and comprehensive evaluations of psychopathology for discriminating between alcoholic subtypes have been infrequent. In a heterogeneous treatment-seeking, outpatient, alcoholic population, we tested the hypothesis that age of onset represents a continuum of disease, and that greater severity of psychopathology is associated with lower ages of onset. Using a standard questionnaire, 253 male and female treatment-seeking alcoholics were stratified according to specific ages of onset: a) <20 years; b) 20-25 years, and c) >25 years. These age of onset groups were compared on alcohol severity and craving, family history, childhood behavior, personality, hostility, overt aggression, mood, and social functioning. Symptom severity and age of onset were negatively correlated, and the 20-25-year onset group usually had intermediate scores. The <20 year onset group was characterized by greater severity of alcohol-related problems, family history, childhood behavioral problems, craving, hostility, antisocial traits, mood disturbance, and poor social functioning. Alcoholics with an earlier age of onset have relatively greater psychopathology than those of later onset. While the preponderance of psychopathology among those in the <20-year onset group could be conceptualized as a clinical 'subtype,' such a characterization would not define an entirely homogenous category. Yet, this clinical characterization would be clinically important if specific age of onset levels were found to be differentially sensitive to pharmacological and/or psychological treatments.