Ninety one neonates received 108 courses of intravenous ceftazidime (25 mg/kg, 12 hourly) over a study period of 15 months. Fourteen had clinically and bacteriologically proved infections. Only one of these had resistant organisms. Four (two with group B beta haemolytic streptococcal infections, one with Escherichia coli meningitis, and one with Staphylococcal aureus septicaemia) failed to respond despite adequate treatment. Bacteriological eradication or clinical improvement, or both, were obtained in the remaining nine. Routine biochemical and haematological values were monitored and there were no side effects. High serum ceftazidime concentrations, well exceeding the minimum inhibitory concentration for most common neonatal pathogens were obtained and maintained throughout treatment. Penetration into the cerebrospinal fluid was excellent in eight of the nine cases studied. Ceftazidime has a theoretical role as a broad spectrum antibiotic suitable for neonatal use with no evident side effects. In this study, however, it was only appropriate for Gram negative infections, and was ineffective against Gram positive organisms. Ceftazidime cannot therefore be recommended as monotherapy before the results of bacteriological culture are known.