The leaching of a fluidised-bed ash with hydrochloric and nitric acids under a variety of conditions has been examined. The rate of extraction of both aluminium and iron increased sharply with increasing temperature and with increasing acid concentration. The effect of the solid: liquid ratio employed was found to be relatively small. In general, the rate of extraction of aluminium was higher using HCl than with HNO3 at the same concentration. Similar recoveries were obtained from both the fluidised-bed ash and colliery tailings which had been calcined under controlled conditions. © 1985.