The report pertains to methanesulfonyl chloride (CAS No. 124-63-0) and is being submitted because of effects observed in a study conducted by multiple exposure routes. The title of the report being submitted is: 'Basic Toxicity of Methanesulfonyl Chloride'. The latter report is being identified as a study involving other than human effects (Unit II.B.2.b of CAP Agreement). Groups of five rats were administered the test compound by gavage at 100 or 50 mg/kg. There was a great decrease in feed intake and body weight gain in both dose groups. All animals in the highdose group died or were euthanatized within six days. No hematology, clinical chemistry or organ weight observations were made for this group. Gross abnormalities in the high-dose group included cytotoxicity of the mucosal surfaces of the gastrointestinal tract and perforation of the wall of the gastrointestinal tract. Toxic hepatitis was observed in all high-dose group animals surviving 24 hours. Abnormalities in the low-dose group included a great decrease in absolute liver and kidney weights and severe necrotizing esophagitis and gastritis with and without ulceration. Lethality with central nervous system (CNS) signs was observed in an acute oral toxicity study in rats and mice. The oral LD, was 50-100 mg/kg in rats and <200 mg/kg in mice. The inhalation 6-hr LC, was 29-132 ppm in rats. This chemical is also a severe skin and eye irritant and it caused a positive dermal sensitization response in 6 of 10 animals tested. This material is used as an intermediate and sold as a pure chemical.