Abstract: In the case of a rotary hearth furnace of annular construction for the heat treatment of workpieces, which has a furnace chamber, an annular rotary hearth, a rotary drive which drives the rotary hearth and a plurality of racks for receiving or supporting workpieces, which are arranged on the annular rotary hearth and are provided with receiving elements, which divide a respective rack into at least two horizontal planes for receiving workpieces, the intention is to provide a solution which makes extremely uniform heating of the workpieces to be heattreated in the furnace chamber possible in a structurally simple and cost-effective manner. This is achieved in that provision is made, at least between two horizontal planes of a respective rack, of at least one additional heating apparatus which heats the workpieces held in the corresponding horizontal planes.