Observations of the radio emission from Jupiter, Saturn, and Mercury at 1.53-cm wavelength are reported. The disk temperature of Saturn was found to be 094 times that of Jupiter at this wavelength. Mercury, observed at an average phase angle of 125 , was found to have a disk temperature three times that of Jupiter. With Jupiter's disk temperature assumed to be 150 K at this wavelength, the temperatures of Saturn and Mercury are 141 and 450 K, respectively. The similarity in the emission from Jupiter and Saturn at this avelength can be explained if one supposes that ammonia gas is the chief source of microwave thermal radiation from both planets (due to the ammonia absorption band centered at 1.28 cm) and that the gas is saturated near the cloud tops of both planets. The possibility that emission from Saturn's rings may contribute to the radio "disk" temperature of Saturn is briefly considered. If the particles in the ring are many centimeters in diameter and perfectly absorbing, the rings contribute about 25 K to the "disk" temperature. If their mean radius is about 300 , a probable size obtained by Franklin and Cook, their microwave extinction cross-section is small and the ring particles will not emit significant microwave energy. The high disk temperature of Mercury at large phase angles is in agreement ith the observations of Howard, Barrett, and Haddock at 3 75 cm and Kellermann at 11 cm. With the radar determination that Mercury does not keep the same face to the Sun (Pettengill), these results can be understood if one supposes that the microwave emission from Mercury is similar to that from the Moon. On the other hand, the lack of disk temperature change with phase angle obtained by Epstein at 3.4 mm does not fit this interpretation.