The uncontrolled disposal of bottom ash from incineration units of hazardous and infected wastes in many countries causes significant scale damage, since it contaminates the soil as well as surface and underground waters, putting both the environment and the public health at risk. In view of the above, a study of bottom ash produced at a hospital medical waste incinerator (HMWI) in Greece was conducted, in order to detect the presence of heavy metals and therefore assess its toxicity; this led to conclusions on the possible contamination of the soil as well as surface and underground waters as a result of its disposal in landfills. The study was conducted at a typical general hospital with 500-bed capacity. About 880 kg of infectious waste coming from a general hospital with all medical departments are pyrolyticly incinerated at the HMWI every day. International literature contains many references to research that characterizes bottom ash as either dangerous, not dangerous, or inert, in an effort to diagnose its proper management and disposal. For this reason, this study focuses on the characterization of bottom ash. Samples were collected from a combustion chamber, over a period of I year, and a series of tests were conducted, including an analysis of particle size distribution, morphology, mineralogical and chemical composition, heavy metal leaching behavior and PCDD/F. (C) 2009 Elsevier B.V. All rights reserved.