This study was performed in order to correlate changes in blood levels of diazepam and desmethyldiazepam with the symptomatology of withdrawal and to examine their elimination kinetics in abusers. The determined half-life of desmethyldiazepam in five diazepam abusers had a wide range of 46.2 to 94.5 hours. Two episodic very high dose abusers exhibited shorter desmethyldiazepam half-lives than was considered normal, possibly due to auto-induction. The half-life of diazepam in a documented very high dose user exceeded that reported in the literature, probably due to accumulation. Withdrawal symptoms reported by the subjects were moderate and included some mental confusion. The most distressing symptom reported was dramatic mood swings which occurred over a matter of minutes. The disappearance of diazepam from blood appears to be the initial cause of withdrawal. Desmethyldiazepam may moderate the severity of the abstinence syndrome but probably lengthens the withdrawal process.