A new parenteral cephem, cefozopran (CZOP), was evaluated for its safety and efficacy in 21 children with acute infections. A mild side effect or an abnormality in laboratory tests was observed in one case each, but the safety of CZOP was otherwise observed. CZOP was effective in all of the 18 bacterial infections tested including pneumonia, cellulitis and urinary tract infections, and all the causative organisms were eradicated. Serum half-lives of CZOP were 1.5-1.8 hours and the urinary excretion rates were 63-96% in the first 5-8 hours after administration. These data suggest that CZOP is safe and effective in children with susceptible bacterial infections.