Barium is occasionally retained in the appendix after radiographic examinations of the gastrointestinal tract, and its significance has been debated for many years. This report details three cases in which barium was present in the appendix at the time of acute appendicitis. Review of these three cases and 13 cases previously reported suggests that retained appendiceal barium may be significant when it exists in either of two patterns. In patients with appropriate symptoms, a barium appendicolith has the same significance as a calcified appendicolith, strongly suggesting a diagnosis of appendicitis. Barium outlining a dilated appendical lumen also suggests appendicitis in the appropriate clinical setting. The significance of retained barium in the appendix in asymptomatic patients remains uncertain.