Abstract: O-Methylhydroartimisinine. (artemether) is one of the effective derivatives of artemisinine (qinghaosu). It has been demonstrated that this compound is a much more potent antimalarial than artemisinine. In order to carry out studies on its physiological disposition and put the dosage regimen design on a rational basis, a sensitive and specific bioanalytical method is required. Determination of MDHA in rabbit plasma by quantitative TLC is reported in this paper. The specificity of the method seemed to be quite good. Lower limit of detection amounted to 0.1 μg. cv was less than 13%, and a total recovery of over 83% was obtained. The results showed that this method well meet the needs of preclinical studies on MDHA.