Procalcitonin can be used in order to differentiate between bacterial and viral respiratory tract infection and to determine the antibiotic treatment length, for the diagnosis and monitoring of patients with sepsis and septic shock and for estimating their prognosis, in order to monitor the response to antibiotic treatment, in order to detect infections in post-surgery and post-organ transplant patients, in patients with severe burns, multiorgan failure and severe trauma, for the diagnosis of sepsis at all ages, including neutropenic patients, for the differential diagnosis of bacterial versus viral meningitis and for the diagnosis of septic arthritis, for the detection of renal involvement in children suffering from urinary tract infections.