This double-blind study was designed to assess the efficacy and safety of fluvastatin-fenofibrate combination therapy compared with fenofibrate monotherapy in severe primary hypercholesterolemia (low-density lipoprotein [LDL] cholesterol > or =190 mg/dl [4.9 mmol/L], triglycerides < or =350mg/dl [3.9 mmol/l]). After a 10-week placebo and dietary baseline period, 102 patients were randomized to receive micronized fenofibrate 200 mg, fluvastatin 20 mg plus micronized fenofibrate 200 mg, or fluvastatin 40 mg plus micronized fenofibrate 200 mg. At week 16, fenofibrate 200 mg alone lowered LDL cholesterol from baseline by 21% compared with 32% for fluvastatin 20 mg plus fenofibrate 200 mg and 41% for fluvastatin 40 mg plus fenofibrate 200 mg (p <0.001). Triglycerides decreased by 29% with fenofibrate 200 mg alone, 39% with fluvastatin 20 mg plus fenofibrate 200 mg, and 40% with fluvastatin 40 mg plus fenofibrate 200 mg (p <0.05). Safety was assessed by recording adverse events and measuring clinical laboratory parameters. The adverse event profile was similar for the 3 treatment groups. One patient withdrew due to an increase in transaminase levels. No significant increase in creatine phosphokinase levels was observed with combination therapy. In conclusion, the addition of fluvastatin to micronized fenofibrate results in substantial improvement in atherogenic plasma lipids and is well tolerated.