There is growing recognition of the value of changing tissue fatty acid patterns in their own right as coronary risk factors. To examine the effects of a conventional nutritional program on plasma triglyceride (TG), cholesterol ester, and phospholipid fatty acid patterns, a group of 20 hyperlipidemic men and a control group (n = 6) of normolipidemic men were followed for 6 months. As an index of change in energy balance in the hyperlipidemic men, body mass index decreased from 26.5 to 24.4 kg m-2 (an 8% decrease) at 6 months. Saturated fat intake fell from 46.7 to 25.3 g/day (a 46% decrease). Dietary polyunsaturated:saturated fat ratio (P:S) rose from 0.38 and to 0.70 (an 84% increase) at the 6-month review. Ethanol intake fell from 18 to 15 g/day (a 17% decrease). Changes in plasma fatty acid (FA) patterns were found in TG, cholesterol ester, and phospholipid fractions at the 6-week to 3-month period, and these changes were maintained at 6 months. Of the factors possibly contributory to plasma FA pattern change in these men, dietary FA intake underwent the greatest percentage shift and therefore probably makes an important contribution to the change. It was of interest that fatty acid patterns in plasma neutral lipids (triglyceride, cholesterol ester, and phospholipid) significantly predicted body mass index and serum total cholesterol, triglyceride, and high-density-lipoprotein cholesterol.