[en] The paper demonstrates the feasibility of a direct contact diathermy applicator operating at 915 MHz. The design is a circular waveguide internally loaded with two orthogonal pairs of forward ridges to obtain circular polarization and two rear ridges with a probe to excite the guide. Two designs were tested: a 15-cm diameter applicator with one annular choke covered with a microwave absorber and a 25-cm diameter applicator with two additional concentric chokes to limit radiation leakage. In delivering a thermally effective specific absorption rate to a planar phantom, leakage levels were less than 5 mW/sq. cm for applicators in direct contact with the phantom. If there is a small spacing between these applicators and planar phantoms, the net power and associated leakage is excessive