Despite the frequency of ulcerative colitis (UC), and numerous studies related to this disease, controversy remains regarding its distribution patterns. It is generally believed that UC starts in the rectum and progresses proximally in continuity to involve cecum along with appendix in 50% of all cases. However, recent endoscopic and histological studies suggest that UC can occur as a discontinuous process. Furthermore, the few existing studies specifically addressing appendiceal histology in UC are divided over whether ulcerative appendicitis (UA) may be seen without cecal involvement (i.e., as a "skip lesion"). To study the appendiceal pathology in UC, and in particular the frequency of UA as a "skip lesion," we retrospectively evaluated 39 proctocolectomy specimens containing appendices removed for UC. Six cases (17%) had obliterated appendices; appendiceal and cecal histologies of the remaining 33 cases were divided into (a) active disease, (b) quiescent disease, or (c) nonspecific or normal histology. Twenty of 39 appendices (51%) showed active disease, four (10%) had quiescent disease, and nine (23%) were either normal or nonspecifically inflamed. After exclusion of one case for inadequate cecal sampling, comparison of cecal and appendiceal histologies showed concordance in 16 cases and discordance in the remaining 16. Of these discordant cases, six had greater disease activity in the cecum and 10 had greater activity in the appendix. Of these latter 10 cases, six showed normal or nonspecific cecal histology associated with active UA. Thus, "skip lesions" of the appendix were detected in 15% of the UC specimens examined.