A method for analysis of antibiotic sensitivity restoration in staphylococcal populations in humans is described. The mechanism of streptomycin sensitivity restoration in staphylococcal populations on the nasal mucosa of 59 patients 7 months after discharging from surgical stationary was studied. Quantitative estimates for loss of superinfecting streptomycin-resistant staphylococci, initial streptomycin-resistant staphylococci and resistance determinants by the initial streptomycin-resistant staphylococci are presented.