OBJECTIVE To demonstrate the utility of postmarketing studies using in-treatment drug and alcohol abusers as informants for assessing the relative abuse liability of sedative-hypnotic drugs. METHODS A survey was conducted that ascertained exposure to a variety of drugs with hypnotic/sedative properties and elicited subjective evaluations indicative of abuse liability. METHODS Complete data were obtained from 297 admissions (78% male) to three addiction treatment sites in the United Kingdom. Subjects were asked 15 questions about 12 different drugs, including five benzodiazepines, three antidepressants, two non-benzodiazepine hypnotics and two antihistamines (plus one fictitious drug). Three of the benzodiazepines (diazepam, nitrazipam, temazepam) emerged as having substantially more abuse liability than any of the other drugs tested, as revealed by higher scores on abuse liability items (purchased on street, taken to get high, like drug, potential for addiction to drug). The antihistamines (chlorpheniramine, diphenhydramine) had lowest abuse liability profiles, while the antidepressants (amitriptyline, fluoxetine, trazadone) and non-benzodiazepine hypnotics (zolpidem, zopiclone) had similar profiles. CONCLUSIONS This pilot study suggests that postmarketing information on hypnotic drug use obtained from drug addicts entering treatment produces data consistent with other measures of abuse liability. The data suggest that the risk of misuse of newer non-benzodiazepine hypnotics may be less than that of benzodiazepine drugs, and similar to that of sedating antidepressants. The new methodology may serve to clarify or validate premarketing abuse liability data, and may help to inform the regulatory process and physician practice.