&NA;A case control study of 150 individuals with colonic symptoms and diverticular disease diagnosed by total colonoscopy was performed to ascertain whether adenomas and carcinomas are detected with a higher frequency in these patients than in matched controls with symptoms but not diverticular disease. Adenomas and carcinomas were seen in 36 percent of the patients and in 17 percent of the controls (P<.001); the overall odds ratio was calculated to be 3.0 (95 percent confidence interval ±1.8). When examined separately, adenomas maintained their significantly higher frequency (27vs.10 percent,P<.001), while no difference was observed as regards carcinomas (9vs.7 percent). The odds ratios for adenomas and carcinomas were calculated to be 3.5±2.5 and 1.4±1.4, respectively. From the fifth to eighth decades there was a fourfold increase in premalignant and malignant lesions in the patient group and a twofold increase in controls. With relation to sex, a statistically significant difference was reached in men but not in women in the sample examined. These data show that symptomatic patients with colonic diverticula have more frequent adenomas, but not carcinomas than symptomatic control matched by sex and age.