The technique and results of arthroscopic surgery for the removal of osteochondral fragments from 1,000 carpal joints in 591 horses are reported. Of the 591 horses, 580 were racehorses (including 349 Quarter Horses and 220 Thoroughbreds). The distal aspect of the radial carpal bone was the most commonly affected site, followed by the proximal aspect of the intermediate carpal bone and distolateral aspect of the radius. More than one carpal joint was simultaneously operated on in 58.9% of the Quarter Horses and in 37.4% of the Thoroughbreds. Marked differences in the amount of damage were noted at arthroscopy, compared with what was observed on radiography. Arthroscopic surgery was an effective technique for removing the osteochondral fragments as well as for treating other lesions. The overall functional ability as well as cosmetic appearance of the limbs were excellent. There was no postoperative intra-articular infection. Postsurgical follow-up information was obtained for 445 racehorses. After surgery, 303 (68.1%) raced at a level equal to or better than their preinjury level, 49 (11.0%) had decreased performance or still had problems referable to the carpus, 23 (5.2%) were retired without returning to training, 28 (6.3%) sustained another chip fracture, 32 (7.2%) developed other problems, and 10 (2.2%) sustained collapsing slab fractures while racing. When horses were separated into 4 categories of articular damage, the performance in the 2 most severely affected groups was significantly inferior. One hundred thirty-three of 187 horses with grade-1 damage (71.1%), 108 of 144 with grade-2 damage (75.0%), 41 of 77 with grade-3 damage (53.2%), and 20 of 37 horses with grade-4 damage (54.1%) returned to racing at a level equal to or better than their preinjury level. In examining the prognosis relative to site of the fracture, the prognosis for both breeds was worst with lesions of the third carpal bone.