Complications in 322 percutaneous subclavian vein catheters placed in 272 children by the infraclavicular approach were investigated prospectively. Ages ranged from 4 days to 15 years. Incidents during catheter introduction occurred in 13 cases, and were more common when insertion was on the right side (p less than 0.01). Nine (2.8%) required urgent treatment: (6 pneumothorax, 1 hydrothorax, and 2 hemothorax). Anomalous lodging of the catheter tip was more common when insertion was on the right side (p less than 0.05). Complications during catheter maintenance were 3 venous thromboses, 3 catheter obstructions, and 7 migrations out of position. There was no significant difference in complications related to age. Catheter cultures were positive in 33 (17%) of 190 catheters cultured (27 through colonization and 6 through catheter-related sepsis). Staph. epidermidis was the organism most frequently isolated (19 cases; 58%). Catheterization time of more than 5 days and catheter-related sepsis were statistically associated (p less than 0.05). Staph. epidermidis isolation and duration of cannula use were statistically related (p less than 0.01). No catheter-related deaths occurred. We conclude that subclavian vein catheterization is a simple and useful procedure that entails relatively few serious complications when performed by experienced pediatricians.