The radiation efficiency of printed circuit antennas due to surface-wave effects is optimized to 100% for lossless materials. This is attained with a magnetic superstrate layer on a dielectric substrate. A combination of substrate-superstrate thickness and material parameters results in the elimination of surface wave modes and, therefore, radiation efficiency optimization. When antennas are printed on a grounded substrate with moderate values of dielectric constant, elimination of surface wave modes and, therefore, 100% radiation efficiency due to material effects can be obtained only with the addition of a magnetic superstrate layer if radiation resistance is to be kept at a useful level.