In a double-blind, randomized controlled trial, children with malignant diseases had their tunneled right atrial catheters flushed with either sterile saline or bacteriostatic saline, once per week for 26 weeks. There was no significant difference in the rates of catheter colonization between the two groups, which did differ, however, in terms of the time from entry into the study to the first infective event (64 +/- 34 days vs. 146 +/- 27 days; p less than 0.001). This was strongly suggestive of a seasonal effect, as all of the colonizations in the bacteriostatic saline group were delayed until the summer months. We conclude that the use of a bacteriostatic saline flush solution for tunneled right atrial catheters is beneficial in efforts to prevent catheter colonization.