1. Single exposures of either condenser field, short wave (8 meters) or microwave (11 centimeters), were applied to the region of the knee joint in approximately fifty albino rats. At varying intervals of time, appropriate animals were sacrificed and examined for changes in bone length, soft-tissue change, and roentgenographic and microscopic appearance of the treated extremity.

2. Soft-tissue injury following large dosages of diathermy showed a general correlation to the applied voltage, but sufficient variation in reaction resulted to make accurate dosage impossible under the conditions of the experiment.

3. When moderate soft-tissue injury was present immediately after exposure to either short-wave or microwave radiation, the subsequent effect on bone growth—shortening, deformity, partial or complete epiphyseal destruction, et cetera—did not always parallel the extent of the soft-tissue injury.

4. An unusual sequela to microwave burn was characterized by extensive bone absorption and resulting flail extremity.

5. In two clinical cases, extensive disturbances in bone growth resulted in children who had received burns following diathermy treatment.

6. Caution should be observed in all diathermy treatments; they may be contraindicated for children.