The prevalence, age at diagnosis, clinical characteristics and treatment of young diabetics, younger than 40 years were determined on the basis of a cross-sectional study of medical records of 2 health districts in Pahang, Malaysia. There were only 20 insulin-dependent diabetics (IDDM), prevalence 0.07 per 1000 inhabitants. There were 84 non-insulin-dependent diabetics (NIDDM), prevalence 0.3 per 1000 inhabitants. Three of the NIDDM patients could have malnutrition-related diabetes. Many NIDDM patients were asymptomatic which is an important reason why many of them remain undetected in the community. Seventy-four percent of the patients below the age of 30 years at diagnosis had NIDDM, 56% of the patients below the age of 20 years at diagnosis also had NIDDM and 54% of the NIDDM patients had a strong family history of diabetes. Many NIDDM patients were misdiagnosed as IDDM, especially if they were underweight, leading to considerable overuse of insulin. This study confirms that IDDM is rare in Malaysia, as in other Asian countries. Most young diabetics have NIDDM and have a strong family history. This pattern of diabetes in the young is unlike that seen in the West.