A urine preservative containing NaCl and polyvinyl-pyrrolidone has been in general use at this hospital for three years. It enables the specimen to be held at room temperature for 48 hours or more without appreciable change in the content of viable bacteria. The results of bacteriological tests performed on 2452 preserved urine specimens are compared with those from a control series examined before the method was introduced. A marked improvement in accuracy is demonstrated. The preservative can be very easily and cheaply prepared in any laboratory.