Increased concentrations of n-3 polyunsaturated fatty acids (PUFA), namely eicosapentaenoic acid (20 : 5; EPA) and docosahexaenoic acid (22 : 6; DHA), have been shown to be beneficial in coronary artery disease (CAD). In the present study, the relationships between fish intake and concentrations of serum EPA and DHA and the effects of these fatty acids on serum lipids and lipoproteins were investigated. Two groups of men, one living in a fishing village and the other in a farming village, participated in this study. The daily fish consumption was ten times greater in the fishing village group than in the rural village group and the mortality from IHD in the rural village was four times higher. Serum concentrations of EPA and DHA were significantly higher in the fishing village group (P < 0·001). In this group, the serum concentration of arachidonic acid (20 : 4; AA), was significantly lower (P < 0·001), and the ratio EPA : AA was twice that of the rural village (P < 0·001). Moreover, in the fishing village group, the serum triacylglycerol and total cholesterol levels were significantly lower than those observed in the rural village (P < 0·01 and P < 0·05 respectively). In the fishing village group the serum LDL-cholesterol concentration was also lower, although the difference was not significant. Our results reinforce the hypothesis that a high intake of n-3 PUFA provides protection against CAD.