The effects of celiprolol on insulin sensitivity, glucose tolerance and serum lipids were compared to those of other antihypertensive drugs (beta- or Ca-blocker or ACE-inhibitor) in 23 dyslipidemic non-diabetic patients with controlled hypertension. Hyperinsulinemic euglycemic clamp and independent oral glucose tolerance tests (OGTT) were performed before and 6 months after the study treatment. Six patients out of 23 were randomized to the control group where antihypertensive monotherapy was kept unchanged. Mean glucose disposal rate (M, mean +/- SEM) determined in the clamp test increased in the celiprolol group from 24.4 +/- 2.3 to 34.9 +/- 2.4 mumol/kg/min (p < 0.001). Insulin sensitivity improved during celiprolol treatment independent of the previous treatment. In the control group, M remained practically unchanged (21.6 +/- 3.7 mumol/kg/min). During 2 h OGTT, incremental glucose and insulin AUC decreased in the celiprolol group from 4.5 +/- 0.7 to 2.0 +/- 0.6 mM*h (p < 0.002) and from 113 +/- 16 to 72 +/- 10 mU/l*h (p < 0.005), respectively. There was also a small beneficial change in serum lipids in the celiprolol group: a reduction in serum total cholesterol (-4%), triglycerides (-11%) and LDL-cholesterol (-9%), and an increase in HDL-cholesterol (+6%) and HDL/LDL ratio (+15%). No significant change occurred in the control group. Fasting serum glucose and insulin did not change significantly in either group. In this study with a limited control group, celiprolol improved insulin sensitivity, glucose tolerance and serum lipid profiles of dyslipidemic hypertensive patients.