The microwave heating rate for a plasma in a d.c. magnetic field is found by multiplying the emission rate for a relativistic electron in a d.c. magnetic field by a correction factor corresponding to the number of incident photons and integrating this expression over a particle velocity distribution. The correction factor which relates the absorption rate to the emission rate is found to be proportional to 1/ω3. The maximum heating rate always occurs below the electron cyclotron frequency. For electron temperatures greater than 50 keV, the heating rate decays as ln ω for frequencies well above the fundamental resonance. The maximum heating rate occurs at a lower frequency for higher-temperature plasmas. The highfrequency tail of the heating rate falls off more rapidly for a loss-cone velocity distribution than for a Maxwellian.