To test the hypothesis that non-sterol mevalonate pathway end products lower serum cholesterol levels, we asked 22 hypercholesterolemic subjects (315 +/- 9 mg cholesterol/dl) to take a daily capsule containing 140 mg of lemongrass oil, an essential oil rich in geraniol and citral. The paired difference in serum cholesterol levels of subjects completing the 90-day study approached significance (P less than 0.06, 2-tailed t-test). The subjects segregated into two groups, one consisting of 14 subjects resistant to the protocol and the other consisting of 8 subjects who responded. Paired differences in cholesterol level at 30, 60 and 90 d for resistant subjects were +2 +/- 6, +2 +/- 7 and -1 +/- 6 mg/dl; paired differences for the responding subjects were -25 +/- 10 (p less than 0.05), -33 +/- 8 (p less than 0.01) and -38 +/- 10 (p less than 0.025), respectively. The paired difference (+8 +/- 4) in the cholesterol levels of six responders 90 days after the discontinuation of lemongrass oil was not significant.