Abstract. 1. 1. There was a marked contrast between a therapeutic dose level (1 mg./kg.) and a toxic level (10 mg./kg.) in the percentage urinary excretion of stilbamidine in rats. 2. 2. Considerably more (in one series of experiments about twenty times) amidine was determined by the glyoxal than by the fluorescence method. 3. 3. By the glyoxal method the daily excretion reached a maximum after about five daily injections of a therapeutic dose. 4. 4. A large proportion of stilbamidine was presumably metabolized and excreted in a non-fluorescent form. The preparation of 2-amino stilbamidine is described by Ashley and Harris (to be published in the Journal of the Chemical Society).