We have determined in 128 diabetic (57 non insulin-dependent (NIDDM) and 71 insulin-dependent (IDDM) patients) and in control subjects, serum total cholesterol, HDL cholesterol, triglycerides and Hb Alc levels. Presence of macroangiopathy was assessed by clinical findings. In IDDM increasingly poor control of diabetes was associated with significant increases in total cholesterol (p less than 0.001) and triglycerides (p less than 0.01). HDL cholesterol (1.19 +/- 0.39 mM/l) did not differ from control subjects (1.30 +/- 0.35 mM/l) and was not related to Hb Alc levels. NIDDM had increased total cholesterol (5.91 +/- 1.45 vs 5.38 +/- 0.93 mM/l, p less than 0.05) and triglycerides (2.06 - 0.32 to 8.80- vs 1.03 - 0.22 à 2.20 mM/l, p less than 0.01) and decreased HDL cholesterol (1.08 +/- 0.44 vs 1.31 +/- 0.36 mM/l, p less than 0.01). These differences could be explained only in part by the overweight of the NIDDM patients. There was no significant correlation in NIDDM between Hb Alc and serum lipids levels but overweight and triglycerides were positively correlated (p less than 0.02) and triglycerides and HDL cholesterol negatively correlated (p less than 0.05). IDDM with macroangiopathy had higher total cholesterol levels than those without (6.44 +/- 1.60 vs 5.29 +/- 1.22 mM/l, p less than 0.01). IDDM and NIDDM with macroangiopathy had slightly decreased HDL cholesterol; however, the diabetic subjects with macroangiopathy were older and had a longer duration of diabetes than subjects without macroangiopathy.(ABSTRACT TRUNCATED AT 250 WORDS)