The reactions to oral ethanol (0.75 ml/kg), IV low-dose diazepam (0.12 mg/kg) and IV high-dose diazepam (0.2 mg/kg) were evaluated over four test sessions in the same 48 healthy young men. The data demonstrated similar subjective feelings after the low-dose diazepam and ethanol, but significantly greater effect after high-dose diazepam. Despite the similarities on subjective feelings, the low-dose diazepam challenge resulted in significantly more impairment than did ethanol on measures of memory, body sway and the evaluation of the passage of time. The similarities in subjective aspects of intoxication for ethanol and low-dose diazepam have potential implications for increasing our understanding of possible enhanced vulnerabilities for abuse of benzodiazepines among alcohol-abusing patients. The trend for similarities in subjective intoxication but greater impairment in motor and cognitive performance after low-dose diazepam compared to ethanol might indicate that subjects might be less aware of their actual levels of performance difficulties after the benzodiazepine. It is hoped that these data will help clinicians understand more about the quality of intoxication with benzodiazepines and the types of impairments likely to be observed.