Abnormal fatty acid metabolism may play an important role in the pathogenesis of essential hypertension (EH). We compared fasting serum free fatty acid (FFA) composition between EH patients and nonhypertensive (NH) subjects, and examined the relationships between fasting serum FFA composition and waist/hip ratio, insulin activity, blood pressure, serum zinc, age, and sex in both groups. We conducted a cross-sectional study of 232 community-dwelling subjects aged between 35 and 60 years: 109 EH patients and 123 NH subjects. Serum FFA was determined by HPLC analysis. The data were analyzed by multivariate linear stepwise regression, stratified analysis, and correlation analysis. In men, EH patients had lower C22:6/C20:5 ratios (n-3 Delta6-desaturase activity index, 7.96+/-8.81 vs. 14.5+/-13.1, p<0.01), polyunsaturated fatty acid (PUFA), n-3 PUFA and polyunsaturated/saturated (P/S) ratios compared with male subjects without hypertension. There were no differences in women. Fasting serum FFA composition was significantly related to many variables, including waist/hip ratio, insulin sensitivity index, and serum zinc (all p<0.05 or <0.01) for all the subjects, and included both age- and sex-related differences (both p<0.05). Compared with NH, EH patients had lower levels of serum zinc (14.9+/-5.00 micromol L(-1) vs. 16.8+/-6.38 micromol L(-1), p<0.05). We concluded that EH patients had marked alteration in fasting serum FFA composition, which was affected by upper body obesity, insulin resistance, zinc deficiency, and high dietary fat, and that the differences were age- and sex-related.