The pathogenesis of gastric cancer (GC), particularly of the intestinal type, is thought to involve a multistep and multifactorial process. Our objective was to determine the rates of transition from early to advanced gastric lesions in a population in Linqu County, China, where the GC rates are among the highest in the world. An endoscopic screening survey was launched in 1989-1990 among 3,399 residents aged 34-64 years with precancerous lesions diagnosed from biopsies taken from 7 standard locations in the stomach and from any suspicious sites. The cohort was subsequently followed, with endoscopic and histopathologic examinations conducted in 1994. Logistic regression analysis was used to estimate odds ratios (ORs) of progression to advanced lesions of various levels of severity as a function of age, sex and baseline pathology. The rates of progression were higher among older subjects, among men and among subjects with more extensive gastric lesions. 34 incident GCs were identified during the follow-up period. The ORs of GC, adjusted for age and sex, varied from 17.1, for those with baseline diagnoses of superficial intestinal metaplasia (IM), to 29.3, for those with deep IM or mild dysplasia (DYS) or IM with glandular atrophy and neck hyperplasia, to 104.2, for those with moderate or severe DYS, as compared with subjects with superficial gastritis (SG) or chronic atrophic gastritis (CAG) at baseline. Our prospective study of a high-risk population revealed sharp increases in the risk of GC and advanced precursor lesions according to the severity of lesions diagnosed at the start of follow-up. Int. J. Cancer, 83:615-619, 1999. Published 1999 Wiley-Liss, Inc.