Recent advances in high speed photodetector and microwave receiver technology make microwave frequency optical heterodyning an attractive approach for the detection of a number of coherent Raman and Brillouin scattering experiments. We have therefore analyzed the sensitivity of microwave frequency optical heterodyne receivers. Experimental tests on a visible wavelength receiver operating at 13.5 GHz confirm the expectation of shot noise limited sensitivity. The relative merits of microwave frequency optical heterodyne detection and the alternative Fabry–Pe´rot interferometry approach are discussed. ©1998 American Institute of Physics.