The 1000-ft-diameter reflector and associated radar equipment of the Arecibo Ionospheric Observatory have been used to obtain measurements of delay and Doppler frequency shift for echoes returned from the planets Venus and Mercury during 1964 and 1965. A number of determinations of radar cross section and angular scattering law for these planets at an operating frequency of 430 Mc/sec have also been obtained. Venus is found to have a mean cross section of 0.14 of its physical cross section with variations of as much as plus or minus 0.08 during the course of the observations in 1964. Its angular scattering law reflects a distribution of surface slopes significantly smoother than for the moon. Mercury displays a radar cross section between 0.06 and 0.07 of its physical cross section and a scattering law very similar to the moon's.