During a 12-month period, an infection rate of 10% with kanamycin-resistant, resistance-factor (R-factor) carrying enteric organisms was observed in 236 infants admitted to an intensive care nursery (ICN), with a mortality of 38%. Maternal and perinatal complications did not predispose to infection. In contrast, a combination of therapeutic procedures (surgery, use of penicillin and kanamycin, catheters, ventilation) was associated with increased risk of infection. About 90% of the infants admitted to the ICN became colonized with the resistant organisms, and intestinal tract and groin showed the highest rate of colonization. The majority of the personnel in the ICN carried the organisms in the intestinal tract and on the hands. Handwashing with hexachlorophene failed to reduce the contamination significantly. While the main source of organisms was the colonized and/or infected infants, transmission probably occurred via the hands of personnel.