The phenotypic and genotypic characteristics of Staphylococcus aureus strains isolated from respiratory tract of cystic fibrosis (CF) patients were investigated. Slime production, cell-surface hydrophobicity, type of capsular polysaccharide, profile of heteroresistance to methicillin and Sma I restriction profiles were evaluated. S. aureus CF strains have been shown to be heterogeneous in respect to several important features. All of them were slime producing with variation in colony morphology. High or moderate cell-surface hydrophobicity (CSH) was found for, respectively, 16.2% and 83.8% strains. Thirty strains were resistant to methicillin, 60% of them showed heteroresitance and 40% were homoresistant. It was found that 59.6% of strains produced capsular polysaccharides (CP) of 5 or 8 type. Among CP5/CP8 strains, CP8 was the predominant type (81.1%). Typing of 62 CF strains by macrorestriction analysis of chromosomal DNA revealed several major types, differing in their SmaI profiles with a similarity coefficient lower than 0.4. Some of the strains isolated from the same patient at different times of hospitalization, as well as strains isolated at the same time from the relatives, were identical in their PFGE pattern.