1. By using Nessler's reagent, it is possible to detect NH(3) into which the urea contained in the urinestain has been resolved, and to demonstrate the urinestain. 2. As the above method is high in the degree of sharpness, and is applicable to decomposed urne, heated one, and one left alone, it is considered the best one for the legal-medical demonstration of urinestain. 3. As the chloride contained in the urinestain is comparatively regularly diffused with the lapse of time away from the circumference of the urinestain, it is possible to judge the degree of oldness of the urinestain by measuring the width of the diffusion of the chloride revealed by means of chloridereaction.