The acute phase protein serum amyloid A (SAA) has become widely used as a diagnostic aid for the early detection of inflammation. SAA increases by more than 25 % in 24 to 38 hours after tissue damage caused by trauma or infection. To determine the increase in serum amyloid A (SAA) following colic surgery and to compare it to changes in leukocyte count, client owned horses > 2 years of age, presented for colic with emergency laparotomy were used. Whole blood SAA concentration and leukocyte count were determined before surgery and at 48, 72, and 96 hours post-surgery. Lesions were classified as non-inflammatory or inflammatory during surgery. 61 horses underwent emergency laparotomy; 44 horses were excluded. Of the remaining 17 horses, 12 had non-inflammatory, 5 inflammatory lesions. Before surgery SAA concentrations in horses classified as non-inflammatory ranged from 0 to 217 μg/mL (median 14 μg/mL, range 10-18) and from 0 to 987 μg/mL (median 162 μg/mL, range 162) in inflammatory cases. In all horses SAA concentrations increased significantly 48 hours post-surgery (p = 0.002), horses with inflammatory lesions had significantly higher SAA concentrations (median 2750 μg/mL, range 1916-2835) compared to non-inflammatory lesions (median 624 μg/mL, range 471-740) at 48 (p = 0.0004), 72 (p = 0.0009), and 96 (p = 0.0007) hours post-surgery. Maximum SAA concentration was observed 48-72 hours post-surgery in all cases. White blood cell count (WBC) revealed a mild decrease post-surgically in some cases. At discharge all horses had SAA concentrations < 200 μg/mL. Differences in SAA concentrations between inflammatory and non-inflammatory cases can be expected. The knowledge of normal postoperative SAA concentrations is essential if SAA is used for monitoring occurrence of postoperative infections.