C-reactive protein (CRP) is used routinely in many hospitals to evaluate patients with an acute abdomen. We assessed CRP levels in non-specific abdominal pain (NSAP) and surgical conditions requiring operative or non-operative intervention. The aim of this study was to identify a level of CRP that can be useful in differentiating these three groups. All patients older than 25 years and admitted with acute abdominal pain other than those requiring emergency surgery were included. CRP within 24 h was assessed in all patients. Various cut-off values (< 6, > 6-50, > 50-100, > 100-150 and > 150 mg/l) were used to identify a useful diagnostic level of CRP in the 3 groups. A total of 211 patients were prospectively evaluated - 129 women and 82 men with a mean age of 62.4 years (range, 27-92 years). CRP was performed in 196 within 24 h of admission. Sixty had NSAP while 136 had a surgical condition, of whom 69 had an operation/intervention while the rest were treated non-operatively. The median and interquartile (IQ) range for the three groups were: NSAP, 16 mg/l and 7.75-85.75 mg/l; surgical non-operative group, 75 mg/l and 30.5-150 mg/l; and surgical-operative, 111 mg/l and 42-212 mg/l, respectively. These results were statistically significant (P = 0.001). NSAP was diagnosed in 61% of patients at levels < 6 mg/l compared to 39% of patients in the surgical groups. At levels > 150 mg/l, NSAP was diagnosed in 15% of patients compared to only 54% and 31% for the operative and non-operative groups, respectively. Despite statistically significant differences between the three groups, no useful level of CRP could be identified to differentiate between patients with NSAP and those requiring operative or non-operative management.