Circulating concentrations of total cholesterol, triglycerides, non-esterified fatty acids (NEFA), glycerol, and 3-hydroxybutyrate (3-HB) were measured in 133 subjects with normal glucose tolerance (NGT), 78 with impaired-glucose-tolerance (IGT) and 189 non-insulin dependent (Type 2) diabetic (NIDDM) patients. Plasma cholesterol concentration was similar in the three groups; NGT (4.2 (2.3-7.5) mmol l-1, median (range)), IGT (4.7 (2.7-6.3)) and NIDDM (4.3 (2.3-6.9)). Plasma triglycerides (NGT 0.88 (0.37-2.80), IGT 1.26 (0.43-3.82) and NIDDM 1.38 (0.62-3.91) mmol l-1) and NEFA (NGT 0.81 (0.29-1.58), IGT 1.02 (0.33-1.87) and NIDDM 1.02 (0.48-2.77) mmol l-1) were higher in the two hyperglycaemic groups, but blood 3-HB concentration was similar in the three groups. Plasma cholesterol concentration in these subjects is lower than that reported in white Caucasians in the UK and USA and migrant Indian NIDDM patients in the UK. In NIDDM patients plasma cholesterol concentration was related to age, body mass index (BMI), and plasma glucose concentration while plasma triglyceride concentration was related to plasma NEFA and insulin (IRI) concentration. Evidence of ischaemia on electrocardiography in patients with diabetes was associated with higher age, blood pressure, plasma triglyceride, glucose, and IRI concentrations.