In Australia intermittent carbamazepine intoxication that occurs around the expected time of the peak post-dose plasma drug concentrations has been seen more frequently in recent years than in the past. Reworking of pharmacokinetic data from earlier studies of the drug suggests that, between 1977 and 1980, there was a change in the absorption profile of carbamazepine in the most widely used oral Australian preparation of the drug. The drug's absorption rate increased and its peak plasma levels occurred earlier. The reason for this altered absorption profile cannot now be traced, but it seems a possible explanation for the clinical problem that has emerged subsequently in a number of patients.