The reinforcing effects of alprazolam were investigated in 14 patients who had generalized anxiety or panic disorder, but were not current users/abusers of other psychoactive substances. Using a double-blind outpatient choice procedure, color-coded alprazolam (0.5 mg) and placebo capsules were provided to patients for use 'as needed' in the treatment of anxiety symptoms. Comparisons of alprazolam and placebo during a 2 week sampling period in which placebo and alprazolam were available sequentially revealed no significant differences on measures of medication usage or anxiety levels, although alprazolam did increase subjective ratings of drug effects side effects. During a 4 week choice period, alprazolam was strongly preferred over placebo in 11 out of 14 patients indicating that alprazolam functioned as a reinforcer. Medication usage ranged from zero to 4.0 mg alprazolam in a day. Variations in daily medication-use were positively correlated with anxiety level fluctuations for a majority of patients. For a majority of patients, the results indicate that alprazolam functioned as a reinforcer without accompanying signs of abuse or addiction.