OBJECTIVES: To determine, in a rural and urban population in Cameroon, the prevalence of the metabolic syndrome (MS) using three definitions and to assess the association between components of the MS, central obesity and HOMA insulin resistance (HOMA-IR) index. METHODS: A representative sample of 1573 adults (638 rural, 935 urban) were interviewed on their personal medical history. Blood pressure and anthropometric measures used standardised methods. After an overnight fast, blood samples were collected before and 2h after an OGTT and plasma glucose, plasma insulin and blood lipids determined. Modified WHO, NCEP-ATP III, and IDF definitions of the MS were used. RESULTS: Central obesity was the most prevalent component of the syndrome, but prevalence varied widely according to the definition used. Hypertriglyceridemia was almost non-existent. The highest prevalence of the MS was with the WHO definition and the lowest with the NCEP-ATP III definition. Central obesity was more tightly associated with components of the MS than was HOMA-IR. CONCLUSIONS: The prevalence of the MS varied greatly by rural/urban residence with the various definitions used. Central obesity appears to be the key determinant of the prevalence of the MS in sub Saharan Africa. Many MS definitions may not be appropriate for African populations.