Infectious complication rates and associated risk factors occurring during peripheral intravenous therapy with Teflon catheters were determined during a prospective study of 286 cannula insertions. Suppurative phlebitis, cannula-related sepsis or suspected sepsis did not occur. Semiquantitative cannula cultures revealed a colonization rate of 10.4% (12 of 115). Coagulase-negative nonadherent Staphylococcus was the most common colonizing organism occurring in 10 of 12 positive catheters. Alpha Streptococcus and adherent coagulase-negative Staphylococcus colonized the remaining catheters. Colonization was not related to the rate of phlebitis, extravasation or cannulation time. No patient- or catheter-related factors increased the risk of colonization. In children in a general pediatric ward the risk of catheter colonization and subsequent sepsis should not be used as reasons for routinely removing complication-free peripheral Teflon catheters at 72 hours.