Abstract: A method has been developed for the assay of mercury in organo-mercury drugs using rapid wet-oxidation method followed by thiourea titration with solutions of mercuric thiocyanate and ferric ammonia sulfate as indicator. The interference of bromine may be eliminated by boiling the solutions for a few minutes. As a titrant thiourea is more advantageous than ammonium thiocyanate since the end point is very sharp at a temperature below 40℃.