Response differences following administration of alcohol between adult males with a positive (FHP) versus negative (FHN) family history of alcoholism have been demonstrated in previous research and are thought to be related to risk for developing alcoholism. If this is so, the pharmacological breadth of addiction risk conferred by a positive family alcoholism history might be studied by determining whether FHP subjects show different responses than FHN to drug classes other than alcohol. We have previously reported on the acute effects of ethanol as compared with secobarbital in FHP and FHN subjects and found that FHP subjects showed greater sensitivity across a variety of subjective measures than FHN subjects for both drug classes. The data reported here are based on an extended data collection period of 3 to 18 hr postingestion, following completion of the acute laboratory portion of the study. Specifically, in the present study, dose-effect timecourse functions for a variety of physiological (heart rate, blood pressure, and breath alcohol level), subjective (analog mood, drug effect, and withdrawal, Subjective High Assessment Scale (SHAS)), and psychomotor measures (Digit Symbol Substitution Test and numeric recall) were examined in FHP and FHN college-aged males for secobarbital (0, 100, 200 mg daily) and ethanol (1g/kg daily). FHP and FHN subjects were matched on light-to-moderate drinking patterns, anthropometric dimensions, age, years of schooling, and drug use. FHP subjects reported more extended intoxication and greater withdrawal effects following both ethanol and the high dose of secobarbital than did FHN subjects. In addition, these intoxication and withdrawal effects reported by FHP subjects persisted longer than effects reported by FHNs; this was true both for ethanol and the higher secobarbital dose. No differences in physiological responses emerged between the two groups in any drug condition. The present study is the first demonstration of extended intoxication and withdrawal differences between these groups and points to the need to further examine extended time periods following drug ingestion, as this may reveal additional parameters across which these family history groups differ.