Peripherally inserted central catheters (PICCs) have become popular for long courses of intravenously administration of antibiotics. Although these devices are generally regarded as safe, thrombotic complications have been associated with their use. In a retrospective review, 51 (2.47%) of 2063 patients who had a PICC placed during 1994-1996 were found to have developed a total of 52 PICC-associated venous thromboses (VTs). Two patients received the diagnosis of pulmonary embolism that was a complication of VT. Risk factors for VT identified by multiple logistic regression analysis were younger age, history of VT, discharge to a skilled-nursing facility, and therapy with amphotericin B. VT is a significant complication of PICC placement. It may occur more frequently than previously recognized and may be complicated by pulmonary embolism. Clinicians should maintain a high index of suspicion, especially for high-risk patients.