The diagnostic utility of C-reactive protein (CRP), procalcitonin (PCT) and interleukin-8 (IL-8) were studied in 66 cancer patients with suspected infection (39 with definite foci of infection, 17 with antibiotic responses without foci and 10 with neoplastic fever without infection) and 26 patients scheduled for chemotherapy. The infection group (n=56) had higher median CRP (91 versus 19 mg/l, P<0. 001), PCT (0.28 versus 0.12 ng/ml, P<0.001) and IL-8 values (27.7 versus 16.9 pg/ml, P=0.032) than the non-infection group (n=36). In patients with suspected infection, only PCT was a good marker to discriminate bacteraemia with an area under the receiver operating characteristics curve of 0.92 (95% confidence interval (CI), 0.77-1. 0), but even PCT was less well able to differentiate between non-bacteraemic infections and neoplastic fever (0.56; 95% CI, 0. 35-0.77). In conclusion, PCT was a good indicator for bacteraemia, but none of the three markers were reliable indicators for minor infections in non-neutropenic cancer patients.