The main objective of this study is to identify the possible hazerdous emissions deriving from uncontrolled and incomplete combustions of biomass fuels that are reviewed based on the results of some investigations. Biomass combustion is a contributor of toxic air pollutants, particulate matter (PM), and greenhouse gases. PM emissions and detrimental metal emissions from biomass combustion, emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from the combustion of different biomass and solid wastes are reviewed.