A method for the in situ removal of mobilizable contaminants, including volatile and semi-volatile organic compounds, from a contaminated unsaturated zone of primarily porous layers of soil, comprising pulsatilely injecting heated pressurized steam into a first location in the zone in order to heat the soil in the zone, and withdrawing the contaminants under subatmospheric pressure from the soil at a second location in the zone. In specific application, the pulsatile injection of steam is used t...