The objective of the present study was to measure serum C-reactive protein (CRP) concentrations in 32 dogs with acute abdomen syndrome at presentation and after 48-72 hr. Data were evaluated to determine if there was an association between CRP concentration and outcome, and if CRP concentration correlated with the white blood cell (WBC) count at both time points. An immunoturbidimetric assay for human CRP, previously validated for use in dogs, was used for serum CRP analysis. Increased serum CRP concentrations were found in 21 dogs at presentation. Fifteen of these dogs had declining serum CRP concentrations by 48-72 hr, but 3 of the 15 dogs were later euthanized. Serum CRP concentrations increased by 48-72 hr in 4 dogs. Of the 32 dogs, 4 were dead or were euthanized prior to the 48-72 hr time point. No significant difference between initial CRP concentration and outcome was found (P = 0.054). Initial and 48-72 hr CRP values taken together were significantly different between outcome groups (P < 0.001). Serum CRP concentrations that were elevated at both time points were associated with a poor prognosis. No correlation was found between CRP concentrations and WBC counts at presentation (P = 0.83); however, a significant correlation was noted at 48-72 hr (P = 0.03). Evaluation of sequential CRP concentrations in dogs with acute abdomen syndrome may be helpful in assessing clinical response to treatment and predicting outcome. Also, serum CRP may be better in detecting tissue injury and/or inflammation at presentation than WBC counts in select cases.