The dependency potential of chlormethiazole has been assessed on the basis of animal studies (rat and monkey) and an extensive analysis of human cases reported in the international clinical literature covering a period of 17 years. The results of the animal studies do not show any major physical or psychological dependence on chlormethiazole. Clinical studies of case reports suggest that the evidence for "primary" dependence on chlormethiazole is weak, as most of the analysable cases had a previous history of alcohol and/or other drug abuse/dependence. Moreover, in a high proportion of these cases there was evidence of simultaneous alcohol and/or other drug abuse. It should be stressed that in this group of patients the dependence on chlormethiazole was invariably reported in connection with long-term out-patient medication, that is, in a way that was not in accordance with recommendations for use of the drug in "dried out" alcoholics and/or drug addicts. Reports of chlormethiazole abuse/dependence from the alcohol/drug addiction indication are may involve a population particularly prone to addiction and, therefore, be unrepresentative for general assessment. Conversely, the findings in animal studies provide indirect support for the favourable clinical experiences with chlormethiazole in the geriatric, psychogeriatric and obstetric indication areas where chlormethiazole has been used extensively for more then a decade in a problem-free manner. The risk which applies to long-term use in alcoholics and/or drug addicts or the emotionally unstable, because of their "dependency proneness", does not seem to apply to the treatment of conditions, such as insomnia and agitation, in the elderly in whom the drug has been found to be very useful by various investigators.(ABSTRACT TRUNCATED AT 250 WORDS)