The increased use of triple-lumen catheters has brought with it an increase in sepsis. We undertook a study to determine whether this increase was related to the length of time a catheter was in place. Culture of the fluid in each of the three lumens of all triple-lumen catheters in the medical intensive care units was done daily for a 6-month period. In 14 of 31 catheters, 28 of 93 lumens showed bacterial or fungal growth. A temporal relationship between the time a catheter was placed and the onset of catheter colonization and patient sepsis was established (p less than 0.01). Catheter colonization preceded sepsis in three of four patients who became bacteremic with the same organisms that were cultured from the lumens and the catheter tips. As a result of this study, centrally placed intravascular lines are now changed every 7 days in our institution with a noticeable decrease in line-related sepsis.