A total of 75 central venous catheters were used for prolonged chemotherapy in 39 children with acute lymphocytic leukemia and 21 patients with acute myelocytic leukemia. Infection rates were 2.2 per 100 catheter days with the use of cuffed, tunneled, single-lumen Silastic catheters, 2.0 per 1000 catheter days with cuffed, tunneled, double-lumen Silastic catheters, and 0.5 per 1000 catheter days with the use of implanted venous access systems. Eighty-one percent of catheter sepsis episodes were successfully treated without removal of the catheter. All tunnel infections required withdrawal of the catheter for cure. The microorganisms were gram-positive bacteria in 15%, gram-negative bacteria in 7%, and fungi in 4%. Coagulase-negative staphylococci and Pseudomonas aeruginosa were the most commonly isolated organisms. Three of six fatal sepsis episodes were caused by disseminated fungal infections. We conclude that the use of intracorporeal venous catheter systems in patients with acute lymphocytic leukemia is associated with a lower infection rate than that with cuffed, tunneled Silastic single- or double-lumen catheters and that most septicemias can be cured with antimicrobial therapy without removal of the catheter.