The minimal fatal dose of the colloidal sulphur preparation (sulphur diasporal) used in the treatment of arthritis was determined by intraperitoneal administration in guinea pigs and intravenously in rabbits. The effects of intravenous administration on the blood pressure and respiration of dogs are reported, as well as the effects of a series of intramuscular injections. These toxicological studies would not indicate that this preparation is harmful in clinical doses.