Abnormalities of epithelial proliferation have been proposed as an early step in gastrointestinal carcinogenesis. To determine whether micronutrient supplementation may reduce squamous epithelial proliferation in the esophagus, we evaluated proliferation in subjects participating in a randomized nutrition intervention trial in Linxian, China, where esophageal cancer rates are among the highest in the world. After 30 months of intervention involving daily supplementation with multiple vitamins and minerals, an endoscopic survey was performed and squamous biopsies from 512 subjects were labeled with tritiated thymidine and autoradiographed. Analysis showed no treatment effect on the overall amount of squamous epithelial proliferation measured by the total labeling index. However, a measure of the vertical distribution of labeled cells showed lower values with supplementation: a 14% reduction in all subjects (P = 0.29), and a 29% reduction in nonsmokers (P = 0.03). These results suggest a potential modest benefit for short-term intervention with multiple vitamins and minerals on squamous epithelial cell proliferation of the esophagus in this high-risk population.