We conducted a prospective study of 6538 polyurethane peripheral intravenous (IV) catheters in 3165 hospitalized adult patients using semiquantitative culture techniques. We found that extending the scheduled catheter replacement interval from 48 to 72 hours to 72 to 96 hours was not a risk factor for local catheter infection, but that catheter insertion by personnel other than IV therapists and the use of continuous infusion to maintain catheter patency were 2 independent risk factors for infection.