Should we screen for colonization to control the spread of multidrug-resistant bacteria? A multidrug-resistant bacteria surveillance program was performed in 1999 at Laënnec Hospital (Nantes, France). After a 3-year period, the results permit us to determine the strategy to strengthen their spread. In 2001, Staphylococcus aureus resistant to methicillin represented 45% of the 202 multidrug-resistant bacteria isolated. The global incidence rate per 100 admissions remained stable between 1999 and 2001 (0.42%), but those of infections acquired in our institution decreased significantly from 0.27% in 1999 to 0.18% in 2001 (P < 0.05), particularly in medical care units (P < 0.04). In spite of this surveillance program and hygiene trainings, the global incidence remained stable during the study period, even if our action contributed to decrease the incidence of S. aureus resistant to methicillin acquired in our institution. Isolation precautions and screening for colonization policy in intensive care units are not sufficient to control the spread of MRB at hospital level. They should be strengthened by procedures for the transfer of infected or colonized patients and by antibiotic use control.