While an organic chemist was attempting to open a glass ampule containing 1.27c of elemental S35 dissolved in 15 ml of benzene, the vial exploded, and the operator was contaminated internally and externally with the radioactive material. It is extremely difficult to measure the effectiveness of therapy employed to encourage the removal of absorbed radioactivity, or to assess with assurance the validity ofour estimation of total body radioactive burden. However, utilizing the techniques of dilution of the absorbed radioactive material with nonradioactive sulfur in several of its many utilized forms, as well as the administration of agents which seem likely to increase the rate of excretion of S35, the major load of detectable S35 was cleared from the body within 5 days. The biological half life of plasma radioactivity was about 19 hr. Approximately 85 per cent of the urinary and 90 per cent of the fecal radioactivity were excreted within 24 hr of the accident. This is in agreement with the classical concept that only a small portion of sulfur introduced in a non-organic form is retained by the body. The observations in this unusual case are discussed in the light of available literature on S35. The body burden has been estimated to have been 13–26 microc. There is ample evidence in the literature to suggest that these quantities of radioactive sulfur are unlikely to cause any radiation damage and, indeed, no adverse effects have been noted during the 3 years since exposure.