Monthly urine cultures were analyzed at the University of Alberta Department of Medical Microbiology and Infectious Diseases to determine whether single-use sterile catheters and clean technique reduced the incidence of bacterial colonization in those using long-term intermittent self-catheterization. Thirty subjects with spina bifida, ages 3 years to 16 years, entered a crossover study with random assignment to 6 months of sterile single-use catheters or clean reused catheters. Seventeen subjects were catheterized by a parent or caregiver; 13 were responsible for self-catheterization and cleaning of the catheters. Six months of descriptive data were also collected at Alberta Children's Hospital from a similar group of subjects with spina bifida who used sterile catheters only. In the crossover group, 38% of all urine cultures were positive regardless of whether sterile single-use or clean reused catheters were employed. The other group using only sterile catheters had a 36% positive culture rate. No difference in positive cultures was found between males and females or between children who catheterized themselves and children whose parents catheterized them. The authors concluded that plastic urethral catheters may be reused.