Eleven hospitalized patients with bacterial meningitis were treated with cefoperazone at daily dosage ranging between 3 and 8 g intravenously. Seven patients had proven Gram-negative bacterial infections, but in four patients the aetiological agent remained unknown. Eight patients completely recovered from infection and the pathogens were eradicated, in one patient the treatment failed and in two patients only some improvement was registered. Furthermore in five patients cefoperazone serum and cerebrospinal fluid levels were determined four times in the first week of treatment (1st, 3rd, 5th and 7th day). No side-effects were recorded. Cefoperazone can be considered as effective antimicrobial agent in the therapy of bacterial meningitis.