This is a retrospective study on the prevalence of diverticulosis in Hong Kong Chinese adults. Eight-hundred and fifty-eight consecutive barium enema examinations over a period of 18 months (January 1995-June 1996) were analysed. Results show that the prevalence of diverticulosis in our community is 25.1% with no significant difference between male and female adults. The prevalence is lower than Western countries but higher than in Asia. Moreover, the peak prevalence is at the 50-79 years age group with lower prevalence in the older age groups. This may be explained by the rapid rise in prevalence in the younger age groups so that the age-related increase in prevalence become obscured. We postulate that this may be due to Western cultural influence in our diet and lifestyle. There is no significant difference in the symptomatology of patients with and without diverticulosis, supporting the idea that diverticulosis alone is usually asymptomatic. There is predominance of right hemicolon involvement in our subjects, in contrast to the left hemicolon predominance in the Caucasian population. Of patients with diverticulosis, 55.3% have only right-sided involvement and 32.6% have bilateral involvement. Only 12.1% of patients with diverticulosis have exclusively left hemicolon involvement. Caecal and ascending colon diverticula are found in 6.4% and 17.6% of all the adults under study, respectively. Clinicians caring for patients from our community should take note of this high frequency of caecal and ascending colon diverticulosis as caecal and ascending colon diverticulitis is notoriously difficult to diagnose clinically.