In clinical practice, when neutropenic-fever patients present with no microbiologically and clinically defined infection, the risk of underestimating an occult infection is of major concern, the clinicians have to make a decision on when to modify antibiotic therapy. Hence, a reliable, specific, and sensitive marker, which is regulated independently from the leukocyte count and the underlying disease, is needed for the early diagnosis of infections in cases of neutropenic fever. We have evaluated the diagnostic and follow-up value of procalcitonin (PCT) compared with C-reactive protein (CRP) and erythrocyte sedimentation rate in documenting the infection in neutropenic-fever patients undergoing intensive chemotherapy, as evidenced by the durational change in these parameters in the presence of defined infection. Forty-nine patients, who had 60 febrile episodes, and who were hospitalized in the Hacettepe University Ihsan Doğramacı Children's Hospital between January 1, 2004 and January 1, 2005 were included in this prospective study. All patients had been diagnosed with neutropenic fever after intensive chemotherapy. In our study, PCT and CRP levels were significantly higher in neutropenic-fever patients (group I and group II separately) than in control patients (P<0.001) throughout the study period; but erythrocyte sedimentation rate levels did not show any significant difference (P>0.05). In sequential analyses of patients without documented infections, the median of PCT concentrations shows a tendency to fall after the 8th hour of onset of fever, whereas in patients with documented infections PCT concentrations fell after the 48th hour. In conclusion, our study suggests that PCT, when measured periodically, is a more useful diagnostic inflammation parameter in pediatric neutropenic-fever patients than CRP, both in estimating the severity of the infection and, the duration and origin of the fever. Hence, PCT might be helpful when deciding on initial therapy modification.