Midstream sampling and colony counts have greatly improved precision in diagnosing urinary tract infections. In women, however, contamination by vaginal flora and cells still poses a diagnostic problem. We have devised an instrument for helping collect uncontaminated urine from women and have tested it in three sets of observations. Approximately 96% of 200 women were able to use the device successfully after minimal instruction. Bacterial colony counts and quantitative estimation of vaginal epithelial cells were performed on urine collected by 18 female volunteers using conventional clean-catch technics and on urine collected by the same 18 women using the Clean Streamer. The average bacterial colony count in conventionally collected urine was 8,100/ml while in Clean Streamer collected urine it was 1,722/mI. The average number of vaginal epithelial cells in conventionally collected urine was 22.4/ml while in Clean Streamer collected urine it was 14. I/ml. The difference in both comparisons is statistically significant (P=.01). We believe that use of the Clean Streamer greatly facilitates the ability of a woman to collect a urine sample uncontaminated by vaginal secretions and flora.