Abstract: In an incinerator of the type having a combustion chamber (10) which may be loaded through a loading doorway (21) and having at least one burner (32) for directing ignited fuel oil or gas and/or combustion air under pressure into the chamber, the combustion chamber (10) is of elliptical shape in plan view, the burner (32) entering the chamber at one end of its long axis and being directed obliquely down to the chamber bottom at its opposite end, the chamber top having a gas outlet (17) at the same end as the burner (32). The incinerator may be of two-stage type, having superimposed on the said chamber, or primary chamber (10), a secondary chamber (11) of similar elliptical shape having at one end of its long axis an entry from the gas outlet (17) of the primary chamber (10), a burner (32) directed obliquely down to the secondary chamber bottom (16) at its opposite end, and an outlet from its top to a flue.