Backgound: Sepsis is the systemic response to infection by microbial organisms. A differential diagnosis of infection caused by either bacteria or other microbial organisms is essential for effective treatment and prognostic assessment. Procalcitonin (PCT) is an accurate biomarker that is effective in identifying patients with sepsis and can be used in the diagnosis of bacterial infections. Objictive: The aim of the current study is to explore the utility of PCT in early diagnosis of sepsis and determine its prognostic role in assessment of treatment response. Patients and Methods: This study included patient group (40 patients with diagnosis of sepsis; 20 males and 20 females with ages ranged from 5-98 years) and 40 control group who matched well with patients as regard age and sex. Study groups was subjected to complete history taking, clinical examination for signs of sepsis, laboratory investigations as Complete Blood Count, C reactive protein, Blood culture, serum Procalcitonin level. Results: The PCT is significantly higher in patients more than the control group. When the CRP values are compared with those of PCT in patients, they both show similar effects in diagnosis of sepsis. PCT indicates an early response for patients to treatment (values were less than 105, reaching the normal level in serum) while CRP values were not indicating any treatment response. Conclusion: Procalcitonin is an important biomarker in the diagnosis of sepsis and it is a useful indicator for the effectiveness of treatment.