Many of the characteristics of typical medical waste ash can be found by using ash leaching experiments. The present study investigated the characteristics of fly ash derived from incineration of medical waste in China. The particle diameter of the fly ash was in the range 154-900 µm. Elemental analyses of the fly ash indicated that it contained calcium, aluminium, iron, sodium, potassium and magnesium, and that copper, lead, chromium and mercury were the dominant heavy metals it contained. As leaching time was increased the leaching concentrations of the heavy metals increased and the leaching toxicity was augmented. When the pH was neutral, the concentrations of most heavy metals in the leachate were minimum whereas when the pH was alkali or acid, the leaching toxicity was greatly enhanced. High temperature melting was found to be a good method of fixing heavy metals, and the main components of the sinter were Fe3O4, SiO2, CaSO4 and CaSiO3, etc.