DIMETHYL sulphoxide (DMSO) has received considerable attention because of its remarkable biological properties1,2, It passes rapidly through many animal membranes, enhances absorption of a wide variety of substances and is also a versatile solvent with little systemic toxicity when given to animals3–5. These properties suggest that DMSO may be used to achieve high tissue concentrations of certain drugs, such as cytotoxic agents, antibiotics and antihistamines. During the investigation of the antihistamines as protective agents against liver necrosis induced by carbon tetrachloride, we found that DMSO in small doses significantly exacerbated carbon tetrachloride toxicity. The present report describes the nature of this unusual property.