The current study assessed whether features of the metabolic syndrome are associated with higher apolipoprotein B(100) (apoB(100)) levels in people with Type 2 diabetes (n = 298) not taking lipid-lowering drugs. Body-mass index (BMI), waist:hip ratio (WHR), urinary albumin excretion rate, presence or absence of hypertension, uric acid levels, and apoB(100) levels were assessed. Both higher BMI and urinary albumin excretion rate were associated with higher apoB(100) levels (1.02 +/- 0.25 ( +/- S.D.) g/l in normal weight, 1.07 +/- 0.22 g/l in overweight and 1.14 +/- 0.25 g/l in obese individuals; P < 0.01; 1.09 +/- 0.23 g/l in normoalbuminuric patients, 1.06 +/- 0.22 g/l if urinary albumin excretion rate 20-50 microg/min and 1.17 +/- 0.27 g/l if urinary albumin excretion rate > 50 microg/min; P < 0.05). An association between the number of features of the metabolic syndrome and higher apoB(100) levels was found (1.03 +/- 0.22 g/l if no features, 1.08 +/- 0.25 g/l if one feature, 1.11 +/- 0.20 g/l if two features and 1.15 +/- 0.27 g/l if > 2 features; P for trend < 0.01). Thus apoB(100) levels show an association with the metabolic syndrome and, hypothetically, to insulin-insensitivity in Type 2 diabetes. BMI (but not WHR) and urinary albumin excretion rate accounted for most of the power of this relationship.