We compared the fatty acid compositions including the n-3 and n-6 polyunsaturated fatty acids families in the red blood cell membranes of 26 healthy normal subjects to those with coronary heart disease. The main finding was a significant decrease in the level of docosahexanoic acid (DHA, 22:6 n-3) in coronary heart disease patients. In addition, an increase in n-6/n-3 ratio, and a decrease in the ratio of 22:6/18:3 (n-3) and in omega-3 index was also observed in coronary heart disease patients. The reduction in 22:6/18:3 (n-3) ratio suggests a defect in the elongation and desaturation steps in the n-3 series. The findings in this study also suggest that the low dietary value of fish from Bahrain water may have resulted in a modest dietary intake of DHA and eicosapentanoic acid (EPA, 20:5 n-3), which might have been the reason behind the high incidence of coronary heart disease in Bahrain.