Two infants, aged 8.5 and 11 months, were admitted for meningitis caused by Streptococcus pneumoniae. Failure of cefotaxime led to the identification of highly penicillin-G-resistant strains. Minimum inhibitory concentrations (MICs) for penicillin were > 2 micrograms/ml, and cefotaxime MICs were 2 micrograms/ml. Both patients rapidly responded to a combination of i.v. imipenem and rifampicin. It is now mandatory to test in-vitro susceptibilities of Streptococcus pneumoniae to penicillin G and other beta-lactam agents when meningitis is diagnosed in infants.