An association between arterial blood pressure and blood viscosity has been suggested in healthy and in diabetic subjects, and that the hemorheological pattern may be influenced by blood lipid alterations. In diabetic patients a relationship between arterial hypertension and blood lipid changes may therefore be suggested. This study concerns 19 type II diabetics with hyperlipidemia (triglycerides = 3.2 +/- 1 mmol/l; total cholesterol = 6.1 +/- 1.2 mmol/l; HDL-cholesterol = 0.92 +/- 0.27 mmol/l; VLDL = 29 +/- 5%) (group A), and 19 normolipidemic type II diabetics (triglycerides = 1.15 +/- 0.5 mmol/l; total cholesterol = 5.1 +/- 1 mmol/l; HDL-cholesterol = 1.25 +/- 0.38 mmol/l; VLDL = 20 +/- 5%) (group B). No differences concerning age, body weight, duration of diabetes and glycemic control were found in hyperlipidemic compared to normolipidemic diabetics. On the contrary, higher systolic and diastolic blood pressure levels were demonstrated in group A (167 +/- 14 mmHg and 101 +/- 5.2 mmHg, respectively) than in group B (144 +/- 15 mmHg, p less than 0.001 and 87 +/- 6.9 mmHg, p less than 0.001, respectively). An increase of plasma apolipoprotein B level (163 +/- 27 mg/dl vs 102 +/- 21 mg/dl, p less than 0.001), of plasma viscosity (1.81 +/- 0.08 mPas vs 1.51 +/- 0.07 mPas, p less than 0.001) and of blood viscosity (5.37 +/- 0.33 mPas vs 5.07 +/- 0.04 mPas, p less than 0.01, at shear-rate of 90 s-1; 18.4 +/- 1 mPas vs 14.1 +/- 0.9 mPas, p less than 0.001 at shear-rate of 2.25 s-1) was found in group A, compared to group B.(ABSTRACT TRUNCATED AT 250 WORDS)