The environmental impact of sewage sludges depends on the availability and phytotoxicity of their heavy metal. The influence of representative sludges (industrial sludge and municipal sludge) on the availability of heavy metals, and their effects on seed germination were compared. The total heavy metal concentrations were below the maximum permitted for land applied waste and the differences among them were small. The DTPA-extracted metal concentrations were significant different. The sum of all the fractions in the slugdes was close to the total metal content as determined by extraction with aqua regia. In addition, there were significant differences in the chemical forms of the heavy metals (Hg, Ni, As, Cd, Cu, Cr, Zn, Pb) by the sequential extraction system. The two different sludges also affected seed germination and root elongation in different ways. The most serious adverse effects were caused by the municipal sewage sludge extract.