The purpose of this study was to evaluate whether lengthening the dwell time of peripheral IV catheters from 72 hours to 144 hours resulted in increased rates of phlebitis and/or infiltration. The study was conducted in medical/surgical units at a 110-bed teaching hospital with an IV team. Kaplan-Meier estimates of the success and failure and conditional failure probabilities were calculated for phlebitis and infiltration scores. Log rank tests were used to test for an association between the covariates and the time until failure. Drug irritation was the most significant predictor of phlebitis and infiltration rates in this study. The total difference in the estimated failure rates for the catheter lasting 6 days versus a new catheter inserted for another 3 days is 1.3%. Because the conditional failure probability estimates for days 4, 5, and 6 are slightly higher than for days 1, 2, and 3, consideration may be given to extending the dwell time of a peripheral IV catheter beyond 72 hours under certain circumstances.