Our purpose was to describe the variation of the radiologic appearance of the carpus of horses of different breeds, discipline, and gender with lameness related to the carpus and control horses, with particular reference to the ulnar carpal bone. Two hundred and eighty-six sets of carpal radiographs from 222 horses were analyzed. Breed, gender, discipline, and cause of lameness were recorded. Chi square tests were used to test for associations between radiologic findings and gender, breed and discipline, to test for associations between different radiologic findings, and to test for associations between radiologic findings and causes of lameness. Bonferroni correction was applied when necessary. The shape of the ulnar carpal bone and most of the anatomic variants, with the exception of the first carpal bone and a radiolucent area in the second carpal bone, were not breed or gender related. Radiolucent areas and associated fragments on the palmaromedial aspect of the ulnar carpal bone can be an incidental finding in horses from all disciplines.