Recently, increasing numbers of gram-negative organisms with multiple drug resistance have been cultured from infants. The majority of these cultures were obtained from areas in which a high percentage of infants were being treated with antibiotics, primarily penicillin and kanamycin. A prospective study was done to determine incidence, age of appearance, and predisposing factors to R-factor cayrrying Enterobacteriacease in the nursery. Cultures were obtained from groin, umbilicus, axilla, nose, throat, eyes, and stool at 12-h intervals for the first three days of life and then daily. Ninty percent of the infants in the intensive care nursery were found to have R-factor carrying bacteria during their stay in the nursery. The mean age of acquiring these organisms was 3.8 days with a range of 1–10 days. The incidence was essentially the same for infants regardless of whether they had been treated with penicillin and kanmycin or no antibiotics. Infants in the regular nursery, many of whom stayed 6 days, had a less than 10% incidence of R-factor carrying gram-negative organisms. These organisms were found only sporadically on the fomites and in fecal and vaginal cultures of the mothers, but could be recovered from personnel working in the intensive care nursery. most of these personnel alos worked in the regular nursery and handled babies who had a low incidence of R-factor carrying organisms. It is presumed that the high incident of R-factor carrying Enterobacteriaceae found in the intensive care nursery is related to the use of antibiotics such as kanamycin in this area. Multiple drug resistance should be looked for in clinical situation such as this and treatment adjusted accordingly.