We investigated the follow-up status and prognosis of 109 patients with non-insulin-dependent diabetes mellitus aged from 10 to 19 years old (66 males and 43 females). Patients who had not attended hospital for at least 20 months up to the end of September 1990 were regarded as defaulters, and were surveyed by questionnaire. There were 62 defaulters (56.9%) among the 109 patients originally enrolled in diabetes care. The defaulters had a significantly higher body mass index (both males and females), mean arterial blood pressure, and fasting blood glucose level than the patients still attending the diabetes clinic, as well as a significantly worse lipid profile. The main reason given for non-attendance was a busy schedule. Compared with patients attending the diabetes clinic, a lower percentage of the defaulters remained on a diet or took regular exercise. Rapid eating was more common among the defaulters than the attendees (92.9% vs. 60%, P = n.s.). Thus, the lifestyle of the defaulters seemed to be undesirable for young diabetic patients. These findings emphasize the importance of effective education and follow-up for young obese patients with non-insulin-dependent diabetes mellitus.