Background: Colorectal surgery is associated with postoperative infectious complications in up to 40\% of cases, but the diagnosis of these complications is frequently misleading, delaying its resolution. Several biomarkers have been shown to be useful in infection diagnosis. Methods: We conducted a single-centre, prospective, observational study segregating patients submitted to elective colorectal surgery with primary anastomosis, CRP and PCT were measured daily. We compared infected and non-infected patients. Results: From October 2009 to June 2011, a total of 50 patients were included. Twenty-one patients developed infection. PCT and CRP before surgery were equally low in patients with or without postoperative infectious complications. After surgery, both PCT and CRP increased markedly. CRP time-course from the day of surgery onwards was significantly different in infected and non-infected patients (P = 0.001) whereas, PCT time-course was almost parallel in both groups (P = 0.866). Multiple comparisons between infected and non-infected patients from 5th to 9th postoperative days (POD) were performed and CRP concentration was significantly different (P < 0.01, Bonferroni correction), on the 6th, 7th and 8th POD. A CRP concentration > 5.0 mg/dl at the D6 was predictive of infection with a sensitivity of 85\% and a specificity of 62\% (positive likelihood ratio 2.2, negative likelihood ratio 0.2). Conclusions: After a major elective surgical insult both CRP and PCT serum levels increased independently of the presence of infection. Besides serum CRP time-course showed to be useful in the early detection of an infectious complication whereas PCT was unhelpful.