A microbiological survey was carried out in two medical Intensive Care Units from January to June 2000. The patients, staff (hands and upper respiratory tract) and environment were monitored. The results obtained in both Care Units give cause for concern. They showed particularly high cultural positivities in bronchoaspirates collected from artificially ventilated patients, a high percentage of positive environmental samples, and frequently contaminated hands in hospital staff, conditions which may facilitate microbial circulation in the medical Intensive Care Units. It would therefore seem necessary to promptly apply specific preventive measures for both the environment and patients.