Previous research has demonstrated response differences following administration of alcohol between adult males with a positive (FHP) versus negative (FHN) family history of alcoholism. These response differences are thought to reflect differences in vulnerability to dependence on alcohol. Thus, the role of positive family alcoholism history in increasing risk of addiction to a variety of drug classes might be studied by determining whether FHP subjects show different responses to drug classes other than alcohol. This was done in the present study by determining dose-effect functions for a variety of physiological (heart rate, skin conductance, skin temperature), subjective (analog mood and drug effect, Subjective High Assessment Scale), and psychomotor measures (hand tremor, body sway, Digit Symbol Substitution Test, eye-hand coordination, and numeric recall) in FHP and FHN college-aged males for secobarbital (0, 100, 200 mg by mouth) and ethanol (1 g/kg). FHP and FHN subjects were matched on light-to-moderate drinking patterns, anthropometric dimensions, age, years of schooling, and drug use. At equivalent blood alcohol levels family-history positive subjects reported greater effects of ethanol than did family-history negative subjects on almost all subjective measures. Following the high dose of secobarbital, FHP but not FHN subjects showed elevated subjective effects; these effects were substantially less and were evident in fewer measures than following ethanol. In contrast to effects on the subjective measures, ethanol and secobarbital produced comparable impairment in both groups of subjects for most psychomotor responses. Group differences were not obtained on any physiological measures.(ABSTRACT TRUNCATED AT 250 WORDS)