One hundred one patients with coronary artery disease and pretreatment ratios of total cholesterol to high density lipoprotein (HDL) cholesterol greater than 4.0 were treated with niacin, commencing at low dosages (100 to 250 mg twice daily) and gradually increasing the dosage over 4 to 8 weeks to 1,000 mg twice daily. Dosage adjustments were made to minimize side effects. At a mean follow-up duration of 11 +/- 7 months, and a mean dosage of 1,415 +/- 698 mg/day, the group had a 13% reduction in total cholesterol, 31% increase in HDL and 32% decrease in the cholesterol to HDL ratio. A subgroup of 62 patients taking greater than 1,000 mg/day of niacin had an 18% reduction in total cholesterol, 32% increase in HDL and 36% improvement in the cholesterol to HDL ratio. A subgroup of 39 patients taking less than or equal to 1,000 mg/day of niacin had only a 5% reduction in total cholesterol, although a 29% increase in HDL and a 24% decrease in the cholesterol to HDL ratio were recorded. Side effects of niacin were reported in 38% of the patients, but led to discontinuation of therapy in only 4. Niacin can be administered in a fashion that is well tolerated, inexpensive and very effective in improving the cholesterol to HDL ratio.