This study was prompted by observing in the summer of 1975, five lethal septicemias caused by methicillin resistant staphylococci. Among the 17 initial S. aureus strains, only 36% were killed at 250 micrograms per ml of methicillin. One phage type of S. aureus predominated (85, group III). Methicillin resistance was found in 17 of 102 S. aureus and in 28 off 102 S. epidermidis septicemias; the mortality among methicillin resistant S. aureus cases was 52.9%, corresponding to 39.3% for S. epidermidis sepsis. Antibiograms revealed methicillin resistance in 59/400 S. aureus and 94/400 S. epidermidis isolates. Cross-resistance to other drugs was common. It is concluded that the emergence of methicillin and gentamicin-tobramycin resistance among hospital staphylococci represents a serious, persistent problem. Certain microbiologic characteristics of these resistant strains differ from results heretofore reported by others.