The susceptibility to antibiotics of 146 strains of Streptococcus pneumoniae isolate from cerebrospinal fluid (CSF) was studied. Seven strains, 3 of the resistant and 4 of the moderately susceptible phenotype, showed similar results for oxacillin by the disk diffusion method and for penicillin by the minimal inhibitory concentration method. Two strains showed opposite results when comparing the two methods. All the other strains (137) were inhibited at an oxacillin concentration of 1 ug/ml by the diffusion disk test.