The clinical efficacy and the pharmacokinetics of cefpirome (CPR, HR 810), a new semisynthetic cephalosporin derivative, were investigated in children with various infectious diseases. CPR showed high blood peak levels, relatively long half-life and high levels in urine. Excellent clinical efficacy was obtained in 2/3 cases with pneumonia, 3/4 cases with upper respiratory infection, 2/2 cases with cutaneous and soft tissue infection and 1/1 case with urinary tract infection. The overall efficacy rate was 80%. No clinical adverse effects were observed while slightly elevated GPT and GOT, decreased platelet were detected in 4 cases without clinical problems. CPR should be an useful and safe drug in treating infectious diseases in children.