Contaminated material is treated with heat and steam to remove halogenated organic compounds from the material. The heating temperature can be lowered by admixing an additive with the contaminated material. A short passage of steam at a flow rate of about at least 0.5 pounds of water by weight per minute per ton of soil immediately following the heating and holding stage, substantially removes the halogenated organic contaminants to below ten parts per million in the treated material.