OBJECTIVE The purpose of this study was to evaluate the level of gallbladder cancer risk associated with polyps and stones of the gallbladder by ultrasound examinations. METHODS We investigated abdominal ultrasonographic findings for gallstones and polyps of the gallbladder and the relationship of these findings to malignancy in 194,767 asymptomatic participants in health screening examinations. RESULTS Gallstones were detected in 7,985 participants (4.1%), at a prevalence of 5.3% in male and 4.5% in female participants. The prevalence was highest in the participants' seventh decade, followed by the sixth and the fifth decades, in both male and female participants. Polyps were found in 10,926 (5.6%), at a prevalence of 6.9% in the male and 4.5% in the female participants. In the male participants, prevalence was highest in the fourth decade, followed by the third and the fifth decades, whereas in the female participants it was highest in the fifth decade, followed by the fourth and third. High prevalence of polyps > or = 10 mm in diameter was found in the fifth to seventh decades in both sexes. Nineteen participants (0.01%) were diagnosed as having gallbladder cancer, and many of them were in the sixth or seventh decade in both sexes. Patients with stones showed a higher prevalence of gallbladder cancer. This difference was shown to be statistically significant by age-adjusted analysis (p < 0.01). The age distribution of the participants with polyps > or = 10 mm in diameter was correlated with that of patients diagnosed with gallbladder cancer. Furthermore, polyp incidence was significantly related to cancer by statistical analysis (p < 0.01). CONCLUSIONS These results suggest an association between gallstone or polyp of the gallbladder and increased risk of malignancy, implying that an etiological association may also exist.