We studied 210 alcoholics, who were re-admitted to a disulfiram treatment programme after having voluntarily discontinued disulfiram therapy, primarily to ascertain whether illness, hospitalization, or serious adverse effects were the cause of the withdrawal. A simple 9-item questionnaire was used. About 70% of the patients gave either "a wish to drink again" or "no need for further treatment" as the reason. Withdrawal in the remaining patients was in no case related to adverse effects of disulfiram. The low incidence of adverse effects was confirmed in another group comprising 93 patients treated under supervision with disulfiram 600-800 mg twice a week for at least a year (i.e. total dose at least 70 g disulfiram). They were monitored by standard laboratory blood and urine tests. There were no clinically significant changes in the measures used. Indeed, many of the patients improved during the year of abstinence. These two studies add weight to the evidence that disulfiram is not a drug with a high incidence of adverse effects.