To obtain fundamental information for prevention of coronary heart disease in young adults, frequency of dietary intake, blood lipid and serum fatty acid compositions were examined for 114 female students. The relationship of selected food intake to serum fatty acid composition was also examined. Results of a nutritional survey were used to identify students who had a frequency of fish intake of "none" or "1-2 times/week" from whom random selection into two groups was accomplished: control group (n = 31) and education group (n = 31). The education group received a recommendation for increasing fish intake for 3 months. The effect of the education program was evaluated by examination of blood lipids, serum fatty acid compositions and frequency of dietary intake. Fifty-four percent of the students reported "none" or "1-2 times/week" for the frequency of fish intake, and 76% of them reported "1 and more times/day" for oil intake. The proportion of serum saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids were 28.9%, 24.4%, 46.8%, respectively. Of the polyunsaturated fraction, 41.4% was omega 6-polyunsaturated fatty acids, and that of omega 3-polyunsaturated fatty acids was 5.4%. The omega 3/omega 6 ratio was 0.13. Serum omega 3-polyunsaturated fatty acids was directly related to frequency of fish intake, and serum omega 6-polyunsaturated fatty acid, especially linoleic acid, was directly related to frequency of oil intake. After a 3-month education program, the frequency of fish intake and meat intake increased, while frequency of oil intake decreased in the education group. Serum omega 3-polyunsaturated fatty acid (in particular eicosapentaenoic acid, docosahexaenoic acid) increased in the education group, but not in the control group. The omega 3/omega 6 ratio increased from 0.13 to 0.18 in the education group. These results indicate that dietary education for fish intake is effective in increasing serum omega 3-polyunsaturated fatty acids, and the omega 3/omega 6 ratio for female students with initial low intake of fish and a high intake of omega 6-polyunsaturated fatty acids.