Abuse liability of diazepam was examined among experienced drug users. The subjects, randomly divided into two groups, each having eight subjects, received diazepam, 15 mg intravenously (gr. 1) and 30 mg orally (gr. 2). Subjective states, drug liking, sedation and euphoria were assessed at pre-drug, 15 min, 120 min and 240 min post-drug administration. In addition, brief assessment to evaluate euphoria and sedation was carried out at 5 min and 45 min for subjects in gr. 1, and at 45 min and 150 min for those in gr. 2. Plasma diazepam level was also estimated. Results indicate those subjects in gr. 1 reported quicker and higher euphoria, drug liking, subjective effects and higher plasma level. The study suggests that route of administration of a compound which has faster onset of action is associated with more liability of abuse.