Two new methods for measuring the reflection coefficient of mercury atoms from a mercury surface are described. In the first, a micromanometer gives both the change in pressure on the surface, and the subsequent rate of evaporation, when a mercury pool is exposed to an opposing liquid air cooled condensing target. From these, reflection coefficients from 0.93 to over 0.99 are obtained. In the second, from measurement of the vapor density between evaporating and condensing surfaces by an ionization gauge, the reflection coefficient can be calculated. With careful purification of the mercury, quite small reflection coefficients result, a mean of 0.2, and a minimum of 0.07 being found. Exposure of the mercury surface to the atmosphere for half an hour brings the reflection up to 0.8, while after 10 days' exposure the reflection coefficient becomes 0.92.