Alkane arsenate herbicides are available commercially, and their acute toxicity has been well documented in previous studies. Animal studies have indicated that dimercaptosuccinic acid (DMSA) can be used as an oral chelating agent. A 20-y-old white male cocaine addict attempted suicide by drinking approximately 500 ml of a 16% monosodium methanearsenate solution. He vomited 10 or more times and was admitted to the intensive care unit with impending shock and early liver and renal involvement. Four 5-day courses of 30 mg DMSA/kg/24 h were given. This brought the serum arsenic level from 2,871 micrograms/L to 6 micrograms/L, and his urine arsenic level from 78,920 micrograms/L to 21 micrograms/L in 30 d. Renal function tests returned to normal, with normal renal creatinine clearance, normal blood urea nitrogen and serum creatinine. However liver functions were abnormal, with elevation of serum transaminases, which later proved secondary to chronic hepatitis. No side effects of DMSA was encountered during the therapy. DMSA was successfully used to detoxify acute organoarsenate poisoning in a clinical setting, supporting experimental reports in the literature.