Cefuroxime was given to 5 neurosurgical patients intravenously in intervals of 8 h. Serum and cerebrospinal fluid (CSF) concentrations were determined periodically over several days. Our results (72 CSF and serum concentrations) show that cefuroxime penetrates the blood CSF barrier to the same low degree as the previously used cephalosporins. In patients with noninflamed meninges the maximum CSF concentration amounted to 0.09 μg/ml, in patients with meningitis the maximum concentration amounted to 8.28 μg/ml. Although these concentrations were achieved, we would recommend cefuroxime only then, if pathogens isolated from CSF are resistant to chloramphenicol and ampicillin or if patients have a penicillin allergy. Cefuroxime is not a suitable drug for perioperative chemoprophylaxis in neurosurgery as used for certain operation