In April-May 2001, a study was conducted to determine the prevalence of antibodies against hepatitis E virus (HEV) among 426 persons 8-49 years of age randomly selected from two groups of rural villages in central Tibet. Group 1 villages were assessed in 1998 as having poor quality water sources; new water systems were then constructed prior to this study. Group 2 villages had higher quality water and were not designated as priority villages for new systems prior to the study. No participants tested positive for IgM; only IgG was detected in the analyzed samples. Overall, 31% of the participants had ever been infected with HEV (95% confidence interval [CI] = 26.7-35.7%). The rate was higher in men (36.6%) than women (26.3%) and highest in those 30-39 years of age (49.1%). The rate of past infection was higher in group 1; the risk ratio was 2.77 (95% CI = 1.98-3.88). This difference is most likely the result of the poor quality of the original water sources in these villages. In resource-poor countries, HEV may be a useful health indicator reflecting the degree of contamination in village water sources. This may be especially important in rural areas (such as Tibet) where maternal mortality ratios are high because HEV may be an important cause of deaths during pregnancy in disease-endemic areas.