VADs are indicated for many persons who require reliable long-term venous access. Nontunneled, tunneled, and venous access ports are constructed of silicone or polyurethane, the most biocompatible materials identified thus far. These devices are inserted in a similar fashion and are extremely versatile. Although VADs represent a major advance in catheter technology, they are not without problems. The most serious and frequently reported complications include infection, thrombosis, and extravasation. Catheter occlusions are another frequent problem, and may be caused by clotted blood or precipitated drug within the catheter. Nursing care centers on prevention and intervention to remove the occlusion. Catheter-related infections may occur at one or more points along the catheter. The most serious are those occurring in the tunnel or as a result of a mural or catheter-tip thrombus. Normal skin flora are most commonly cultured with catheter-related infections. These organisms may be introduced into the body through the catheter hub or less often by migrating along the external catheter. Infections differ in their severity, prognosis, and treatment. Actions to minimize risk (scrupulous care and patient teaching), prompt recognition, and appropriate interventions are crucial. Thrombotic events include fibrin sheaths, patchy thrombotic plaques on the cannulated venous intima, and totally occlusive mural thromboses. Problems associated with these can range from withdrawal occlusion to obstruction of the great vessels and symptoms of superior vena cava syndrome. Mural thrombosis, which probably occurs more frequently than previously suspected, is the most significant risk factor for infection and may also potentiate extravasation. Prompt initiation of therapy will resolve symptoms and maintain the functioning of the catheter. Extravasation can result in transient discomfort or major tissue damage, pain, and functional loss. Needle dislodgment from ports is the most frequent cause. Adequate stabilization of needles and use of nonsiliconized needles are recommended to decrease this risk. Thrombosis at the catheter tip with back tracking of infusate out of the vein to subcutaneous tissues is the second most frequent cause of extravasation and has been reported with tunneled catheters as well as ports. It should be noted that catheter-tip displacement and catheter damage infrequently lead to extravasation. When extravasation is suspected, the infusion is stopped, and the nurse notifies the physician so diagnostic procedures and treatment can be initiated. Other complications occur infrequently but may contribute to patient discomfort, morbidity, and mortality. These include phlebitis, which resolves with conservative management in most instances, and pneumothorax, which occurs in a small percentage of patients within a short period after catheter placement.(ABSTRACT TRUNCATED AT 400 WORDS)