In a study over 15 years, 740 episodes of diabetic ketoacidosis occurred in 505 patients. A total of 113 patients had more than one episode. The majority (90%) of recurrences were within 4 years of the initial episode. Taking a definition of recurrent ketoacidosis as three or more episodes within 4 years, 39 patients were identified. Two subgroups appeared prone to such frequent recurrences, namely girls less than 20 years of age and women more than 59 years of age. A variety of causes of recurrent episodes was noted in the young patients but in the older patients other chronic illnesses complicated the diabetes. The need for good domiciliary supervision of elderly chronic sick patients who require insulin is emphasized.