Objective. To describe the characteristics of youth-onset noninsulin-dependent diabetes mellitus (NIDDM) at diagnosis and compare them with youths with insulin-dependent diabetes mellitus (IDDM) when matched for age, sex, and geographic region of residence. Study Design. Medical records of youths referred for evaluation of diabetes to a pediatric tertiary care center from 1988 to 1995 were reviewed to identify youths diagnosed with NIDDM. Patients selected for study met National Diabetes Data Group criteria for type of diabetes. Results. Fifty patients with NIDDM were reviewed and compared with similar IDDM patients. The NIDDM female:male ratio was 1.6:1 and 74% were African-American. Only 18% of the IDDM patients were African-American. The mean body mass index +/- standard error at diagnosis of NIDDM patients was 35 +/- 1.1 kg/m(2) in contrast to IDDM, 20 +/- .8 kg/m(2). Ninety-six percent of NIDDM and 24% of IDDM youths had a body mass index greater than or equal to 85th percentile. More then 30% of NIDDM youths presented with hypertension. Diabetic ketoacidosis was present in >25% of NIDDM patients. Acanthosis nigricans was documented in 86% of NIDDM and 0% of IDDM patients. Conclusions. In Arkansas, youths with NIDDM are characterized by significant obesity in contrast to youths with IDDM. Physical characteristics such as obesity, acanthosis nigricans, and hypertension on examination of any youth with new-onset diabetes should raise suspicion of NIDDM.