Although there are clearly identifiable withdrawal syndromes following cessation of a number of abused drugs such as alcohol and heroin, it is unclear whether a withdrawal syndrome follows the cessation of crack cocaine. A laboratory model of withdrawal from smoked (crack) cocaine would provide a safe and systematic method of testing the efficacy of behavioral or pharmacological treatments for withdrawal symptoms following cocaine smoking cessation. Therefore, this study investigated acute behavioral, subjective, and physiological withdrawal symptomatology for 6 hrs following 7 deliveries of 2 dose sized (0.07 vs. 0.4 mg/kg) of smoked cocaine. The behavioral measure was performance on a computerized reaction time task, subjective measures included participant and observer ratings of mood and withdrawal symptomatology, and physiological measures comprised heart rate and blood pressure. It was hypothesized that signs and symptoms of withdrawal from smoked cocaine would be greater following the 0.4 mg/kg dose size, compared to the 0.07 mg/kg dose size.