Twenty-eight patients with osteoarticular infection, were treated with a continuous irrigation suction system after surgical debridement. The mean age was 48 years (17-80 years). The average irrigation time was 11,7 days (6-16 days). After the surgical procedure, a bacteriological analysis of irrigation fluid was made every 3 or 4 days. The bacteriological study was qualitative and quantitative. The results showed that 22 patients (78,5%) had a colonization of the irrigation fluid by microorganisms different from the initial microorganism. In 11 patients (39,3%) the colonization was polymicrobial. The incidence of colonization of the system, increased with the irrigation time: 7,4% at third day, 22,2% at sixth day, 63,1% at tenth day and 87,5% at fourteenth day (quantitative cultures). This increase was more notable between the sixth and the tenth day.