Plasma lipid peroxide levels, hereafter referred to as PLP levels, were measured in a group of 40 apparently healthy controls and 64 cholelithiasis patients, 40 with and 24 without jaundice. Hepatic lipid peroxide (HLP) levels were also measured in 26 patients, 15 with and 11 without jaundice. There was a significantly higher mean concentration of PLP in the jaundiced patients than in the control or jaundice-free cases. However, the difference in PLP levels between the jaundice-free and the control cases was insignificant. Meanwhile, patients with jaundice had significantly higher HLP levels than those without jaundice. In the jaundiced cases, the increased PLP and HLP levels were clearly related to the serum levels of bilirubin respectively. In addition, the HLP levels were positively correlated with the PLP levels; however, in the non-jaundiced cases, there was little evidence of these two relationships. Patients with or without jaundice had lower plasma vitamin E levels in comparison to the control cases. The correlation of plasma vitamin E and PLP levels was weak in all of the jaundiced. However, when we subdivided the jaundiced into two groups, the correlation was strong in those with plasma vitamin E levels < 8.5 micrograms/ml, while the correlation was weak in those with plasma vitamin E levels > 8.5 micrograms/ml. Consequently, these results suggest that there is an involvement of lipid peroxidation in liver cells damaged by obstructive jaundice in cholelithiasis patients and there exists a negative correlation between low vitamin E and lipid peroxide levels in plasma.