['To determine the effects of fish oil supplementation on plasma cholesterol in middle-aged men with isolated hypercholesterolemia.', 'Randomized double-blind placebo-controlled (safflower oil) two-period crossover trial with 12-week treatment periods.', 'Outpatient general medicine clinic at a university-affiliated Veterans Affairs hospital.', 'Thirty-eight men with plasma cholesterol between 5.68 and 7.76 mmol/L (220 to 300 mg/dL), triglyceride levels less than 3.39 mmol/L (300 mg/dL), and free of coexisting diseases.', 'Fish oil and placebo (safflower oil) supplementation. After basal measurements and a 4-week lead-in period, twenty 1-g capsules of either fish oil or placebo oil were provided for 12 weeks (period 1). After a 4-week washout phase participants then received the other oil for an additional 12 weeks (period 2).', 'Blood was drawn at the beginning and end of each study period and analyzed for levels of total cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, apolipoprotein A1, and apolipoprotein B. Low-density lipoprotein (LDL) cholesterol was calculated using the Friedewald equation. Total and LDL cholesterol increased from the before treatment values by 4.8% and 9.1%, respectively, after ingestion of fish oil. Compared with placebo, LDL cholesterol was significantly higher (4.5 compared with 4.1 mmol/L, P = 0.01) and triglycerides lower (1.3 compared with 1.8 mmol/L, P = 0.01) after fish oil. Total and HDL cholesterol and apolipoprotein A1 and B levels did not differ.'] Does fish oil supplementation lower plasma cholesterol in men with hypercholesterolemia . Results of a randomized , placebo-controlled crossover study?