Ash (FBA) from an atmospheric fluidized bed combustion (AFBC) unit similar to a western Maryland plant under construction was characterized chemically. Solid-phase samples were analysed for mineral content, elemental composition and potential toxicity. A shake test and two column experiments using different solid and liquid phases estimated leaching from solid phases under different field conditions. The FBA leachate was clean and passed currently accepted standards; elemental analyses also indicated that the FBA tested was clean. A shake test illustrated differences in analytes among FBA, overburden and an FBA-overburden mixture as well as three eluents. All Ag, As, Cd, Hg and Se levels were either below or only rarely above detection limits. In column experiments 1 and 2, tests with four solid phases and four eluents indicated that the potential for detection of Ag, As, Ba, Be, Cd, Cr, Cr6+, Cu, Ge, Hg, Mo, ph and Se in FBA leachate was low. FBA tested in these experiments was clean with respect to trace metal contamination and appeared to be suitable for mine disposal. The results must be viewed with caution since only a single FBA sample was tested.