The emerging concept that various fat compartments are metabolically active and play separate and decisive roles in the pathogenesis of coronary atherosclerosis, hypertension, insulin resistance, diabetes and stroke, has given obesity research a new direction. Of particular interest is the relative amount of intra-abdominal fat thought to be responsible for the metabolic complications. We studied the precise fat distribution and its correlations with the metabolic parameters in 44 non-human primates (Macaca fascicularis). Intra-abdominal, subcutaneous, and total abdominal fat (IAF, SAF, TAF) were assessed by magnetic resonance imaging (MRI) and somatometry. Quantitative computer analyses of abdominal MRI scans revealed predominant IAF distribution. 130x plot analysis of IAF and SAF revealed wide diversity in the amounts of fat, especially in monkeys with body mass index (BMI) < 30 kg/m2. Primates with similar BMI in each quartile revealed an extensive heterogeneity in IAF as well as SAF. Numerous significant correlations within site-specific somatometric measurements as well as within the MRI determinants of abdominal fat were seen. However, only body weight correlated with IAF and skinfolds could predict SAF. After adjusting for body weight, partial correlation analysis showed a significant correlation (P < 0.05) between total cholesterol and IAF. Conclusion: MRI revealed considerable heterogeneity of IAF, SAF and TAF in a cohort of primates believed to be homogeneous by somatometric definition. Male cynomolgus monkeys appear to be a valuable model for a systematic evaluation of fat. Individuals with identical body weight and height may show a diverse pattern of fat distribution.