Colic was treated surgically in 576 horses (545 individuals). Twenty-seven horses were subjected to surgery twice and two horses three times during the period of this study. A total of 371 horses (64.4%) were discharged from the hospital, 205 animals (35.6%) died or were euthanised; 16 of them died during anaesthesia, 102 horses were subjected to euthanasia during surgery, 24 patients did not recover from anaesthesia after surgery completion, and 63 horses did not survive the postoperative period. Ileus of the small intestine was diagnosed in 267 cases (46.4%), affection of the large colon in 239 cases (41.5%), lesion of the small colon in 22 cases (3.8%), lesion of the caecum in 19 cases (3.3%), and affection of stomach and rectum in four and one cases, respectively. In 14 animals (2.4%), lesions were located at two different sites of the gastrointestinal tract. In four horses, the cause of colic was located outside the gastrointestinal tract. Three animals were affected by diffuse peritonitis. No gastrointestinal lesion could be identified during surgery in three horses with recurrent colic. The most common causes of small intestine ileus included incarceration in inguinal hernia (50 of 267 horses, 18.7%), hernia of the omental foramen (31 of 267 horses, 11.6%), anterior enteritis (19 of 267 horses, 7.1%), mesenterial volvulus (18 of 267 horses, 6.7%), and ileal impaction (18 of 267 horses, 6.7%). The most common caecal disorder was acute constipation/dysfunction (5 of 19 horses, 26.3%). Frequent causes of the large colon colic were torsion (63 of 239 horses, 26.4%), left dorsal displacement (36 of 239 horses, 15.1%), and right dorsal displacement (23 of 239 horses, 9.6%). The small colon was most often affected by focal obstruction/constipation (9 out of 22 horses, 40.9%). Surgical treatment of colic of the small intestine, caecum, large colon, and small colon was successful in 59.6%, 36.8%, 73.3%, and 63.6% of the cases, respectively.