Six hundred fifty-four peripheral Teflon catheters in 303 pediatric intensive care unit patients were examined to determine complication rates and associated risk factors. Phlebitis, extravasation, and bacterial colonization occurred at rates of 13%, 28%, and 11%, respectively. Logistic regression of factors that increased phlebitis risk revealed infusion of hyperalimentation (odds ratio 2.9) or lorazepam (odds ratio 2.2) and catheter location (odds ratio 2.9) as the most important determinants of phlebitis risk. Age (less than or equal to 1 year, odds ratio 2.0), catheter time in situ (less than or equal to 72 hours, odds ratio 2.1), and infusion of antiepileptics (odds ratio 2.1) were the most important determinants of extravasation. Catheters were colonized most frequently with coagulase-negative Staphylococcus (51/54). Sepsis attributable to catheter colonization occurred in 1 patient. Duration of catheter placement (greater than or equal to 144 hours, odds ratio 5.8) was an important determinant of catheter colonization. Colonization risk increased from 11% in catheters that were in situ for 48 to 144 hours to 34% for catheters that were in for longer than 144 hours. Infusion of diazepam (odds ratio 11.0) or lipid emulsions (odds ratio 2.5) and age (less than or equal to 1 year, odds ratio 2.2) were also important determinants of colonization risk. Replacing catheters in critically ill children every 72 hours would not decrease phlebitis, bacterial colonization, or catheter-induced sepsis and could increase extravasation risk. Catheters can be safely maintained with adequate monitoring for up to 144 hours in critically ill children.