A strain of Staphylococcus aureus producing toxic shock syndrome toxin-1 was repeatedly isolated from the nares of a neurosurgeon. This strain was identical to strains cultured from two of his patients who developed toxic shock syndrome after laminectomy. The relatedness of the isolates was shown by Southern blot hybridization analyses using chromosomal transposons as probes. This approach should be considered, in addition to standard bacteriologic techniques, as an effective method to analyze the relatedness of nosocomial isolates.