The proconvulsive tendency of the novel carbapcnem, meropenem was compared to that of imipenem, alone and in combination with cilastatin. The potentiation of metrazole-induccd convulsions in mice was measured. Both imipenem and imipenem/cilastatin caused significant potentiation of metrazole-induced convulsions at a dose of 200 mg/kg, iv. In contrast, meropenem (50-400 mg/kg, iv) failed to exhibit any significant potentiation of metrazole-induced seizures.