The study is carried out to estimate the efficiency of Procalcitonin in the diagnosis of bacterial infection in cancer patients at Chemical and Radiation Therapy Center in Tishreen University Hospital in Lattakia between 3/1/2015-28\3\2016. This study has included 45 patients, 25 with infection and 20 without infection, all of them have a fever and don't take antibiotics. The all of patients has undergone a comprehensive initial assessment included history, physical examination, biochemical parameters and X-ray images. Procalcitonin was also measured during fever and compared with C-reactive protein CRP, the results indicated that there is a significant correlation between Procalcitonin and infection, where the median values Procalcitonin in patients with infection 16.9 ng/ml compared to 0.7 ng/ml in patients without infection, Procalcitonin concentration was also associated with the severity of the infection, the study showed that the Procalcitonin is more sensitive and specific of the CRP in diagnosing of sepsis in cancer patients.