The mass sensitivity of a 200 MHz surface acoustic wave (SAW) quartz crystal microbalance (QCM) has been determined by comparison with a 10 MHz shear wave (SW) QCM. The calibration technique consisted of exposing the SW QCM and SAW QCM to the same impinging molecular flux, assuming the same rate of deposition on both surfaces, and comparing the change of frequency for the two QCMs. Although the major objective was to determine mass sensitivity at ambient temperature sensitivity was also measured for a range of temperatures between 130 K and 300 K. The materials used to provide the molecular flux were Coray 100 mineral oil, DC 704 silicone oil, and Rheolube R2000 synthetic grease. The mass sensitivity of the SAW QCM measured at 300 K is on the order of 50 Hz.cm2/ng. Mass sensitivity was observed to decrease with temperature, with the lowest value measured being about 39 Hz.cm2/ng at 130 K for Coray 100. The theoretical expression describing the mass sensitivity of the SAW QCM contains two terms, for mass and material elasticity, respectively. The observed decrease in response at lower temperatures (i.e., reduced elasticity) confirm that the material elasticity term, typically ignored at cryogenic temperatures, must be incorporated cryogenic temperatures.