1. In Crocodylus niloticus the liquid urine contains a white deposit. In the present study both the liquid and the deposit have been analysed.
2. For the liquid urine, the following values for percentage of total nitrogen have been found: ammonia, 66.8%; urea, 12.5%; uric acid, 2.3%.
3. For the deposit the corresponding figures are: ammonia, 6.0%; uric acid, 88.6%; urea absent.
4. From the relative proportions of liquid urine and deposit it is calculated that the total excretory nitrogen (liquid + solid) is distributed as follows: ammonia, 25.4%; urea, 4.5%; uric acid, 68.5%.
5. Crocodiles are thus ammono-uricotelic. The view that alligators are ammonotelic derives from analysis of liquid urine only. Uric acid deposits have been noted in the urine of reptiles of many orders and it is probable that they occur also in the urine of alligators.