Examination of 278 newborn infants, parturients, and medical personnel in two maternity hospitals revealed a high level of Klebsiella colonization of all examined biotopes of infants (the nasal cavity in up to 36.5% of cases) and the skin of the mammary glands of nursing mothers (in 36.2% of cases). In the intestine and the nasal cavity of parturient women and medical personnel Klebsiella could be detected 3-10 times more often than in the same biotopes of nonhospitalized pregnant women. From 254 objects of the hospital environment Klebsiella were isolated in 9.05% of cases. The possibility of the transmission of Klebsiella in hospitals by patients with inflammatory processes in their genitals were established. The diversity of the serological picture of strains of most K-serovars and a short period of their isolation were shown. In one hospital serovar K10 with some features of a "hospital" strain was isolated. The strains under study were sensitive to aminoglycosides, cephamesine, chlorhexidine, but resistant to semisynthetic penicillins and chloramine.