The incidence of adenocarcinoma of the esophagus and gastric cardia has been rising rapidly in Western Europe and the United States, especially among white males. Previous reports, based on case series, have suggested an association between colonic neoplasia and Barrett's esophagus, a metaplastic condition of the lower esophagus that can lead to adenocarcinoma. We analyzed cancer incidence data from 1973 to 1989 from the nine population-based registries of the Surveillance, Epidemiology, and End Results program of the United States National Cancer Institute to investigate this association, using malignancies as an outcome. Using a case-control design, we measured the odds of being diagnosed with colorectal adenocarcinoma some time in life among persons diagnosed with adenocarcinomas of the esophagus or gastric cardia relative to persons diagnosed with squamous cell carcinomas of the esophagus. Among white males the odds ratio was 1.44 (95% confidence interval, 1.03-2.02). This association appeared to be independent of which cancer occurred first. In contrast, white females with adenocarcinomas were less likely to be diagnosed with colorectal cancer than those with squamous cell carcinomas (odds ratio, 0.39; 95% confidence interval, 0.19-0.78). These associations appeared to be specific for colorectal tissue because there was no relationship between histological type of esophageal cancer and prostate cancer in men or breast cancer in women. We conclude that men with esophageal adenocarcinoma may be more likely to be diagnosed with colorectal cancer in their lifetime than expected; the opposite association may exist for women.(ABSTRACT TRUNCATED AT 250 WORDS)