In this study 27 healthy dogs were spayed using cable ties as amethod of ligature of ovarian pedicles and uterine stump. Theywere divided in two groups, 18 adults (age: 11 months-7 years)and 9 young females (age: 3-9 months). Blood samples were col-lected from both groups to evaluate the protein fractions (acutephase proteins) in serum before the surgery (BS) and six monthsafter the surgery (AS) by electrophoresis in sodium dodecyl sul-phate-poliacrylamide gel. This study was approved by the AnimalExperimentation Ethics Committee (AEEC). Both groups showeda significant decrease in the results for ceruloplasmin concentra-tions six months after surgery (adults: BS 69 ± 30 mg/dL and AS35 ± 32 mg/dL, P = 0.003; young females: BS 74 ± 22 mg/dLand AS 47 ± 13 mg/dL, P = 0.017) indicating a possible relation-ship between the synthesis of this protein and the absence of 17-beta estradiol. The young females showed a significant increaseof alpha 1-antitrypsin after ovariohysterectomy (BS294 ± 113 mg/dL and AS 391 ± 125 mg/dL, P = 0.008). In thiscase, age may be responsible for this change. No statistically dif-ferences (P > 0.05) in transferrin, haptoglobin and alpha 1-acidglycoprotein concentrations were identified between groups.However, further investigations are needed to evaluate theeffects of ovariohysterectomy in acute phase protein concentra-tions over a shorter period of time. ; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)