Although the value of using experimental animals in the study of radium poisoning is recognized, few studies of experimental radium poisoning have been reported (1, 5). We have studied the excretion of radium from mice by a new method and, in addition, have investigated the possibility of influencing excretion of radium by administration of British antilewisite, 2,3-dimercaptopropanol (hereafter referred to as BAL). This compound has previously been found to be of value in the treatment of arsenic (6), mercury (7), and antimony (8) poisoning. Experimental Procedure The study of the excretion of radium from the body of experimental animals has always involved tedious methods, such as the measurement of exhaled radon, collection of feces and urine, and the ashing of tissues. A more convenient way is to administer equal doses of radium element to each of a large group of animals, kill several animals at fixed periods after radium administration, seal the animals in glass containers, and measure the gamma radiation a month later. In addition to its simplicity, this method offers the further advantage that the individual tissues can then be studied for radium content and biologic changes progressing from the first day after administration. One hundred and fifty C3H male mice between five and six months of age were divided into three groups of 50 each. The mice of all groups were injected intraperitoneally with 0.2 c.c. of an aqueous solution, adjusted to pH 5 with HC1, containing approximately 50 micrograms per cubic centimeter radium element as RaBr2 and 200 micrograms per cubic centimeter of BaCl2. The BaCl2 was included to insure complete solution of the RaBr2. Samples of solution were taken for measurement, and two mice of each group were killed and sealed in glass tubes containing 40 per cent formaldehyde immediately after injection to ascertain the dosage. The mice were kept in cages with wire mesh bottoms and walls to prevent contamination of the fur by excreta. To study the effect of BAL on radium elimination in the early stages of radium poisoning, the first group of animals was given 0.5 mg. BAL in 0.05 c.c. of sesame oil subcutaneously daily for twenty days beginning two days prior to injection of radium. Beginning with the radium injection and continuing for ten days, two mice were killed daily and sealed in glass tubes containing 40 per cent formaldehyde. After this, two mice were killed every second day for ten days and prepared in the same way. Following this, two mice were killed every fifth day for twenty-five days. The remaining mice were kept until death. The second group of mice was used to observe the effect of BAL on radium elimination in the late stages of radium poisoning. Beginning the twentieth day after injection of RaBr2, these animals were given BAL subcutaneously in the same amount as that received by the first group. These injections were continued for twenty days.