Two heavy matals-contg. sewage sludge were studied for chem. compn. and toxicity and then gasified at 298-523 K and air excess 0.12-0.27. The solid and liq. gasification products were studied for toxicity against Vibrio Fisheri bacteria (luminescence method). The toxicity of sewage sludge and solid gasification by-products increased with increasing trace elements content. The tars were toxic in both cases.