It is assumed that the nonthermal radio continua in the terrestrial and Jovian magnetospheres result from conversion of observed upper hybrid waves into o mode waves. The only favorable conversion mechanism for the escaping terrestrial continuum is coalescence with low-frequency waves, and the most favorable waves are ion-cyclotron waves, which should be generated under conditions similar to those required for generation of upper hybrid waves. It is suggested that the Jovian continuum is in a steady state in which the conversion process is balanced by the inverse process, and it is shown that the implied steady state level is reasonably consistent with observations. To account for the observed spectrum of the Jovian continuum requires that the plasma pressure should be approximately constant over a range ne≈102m-3 to 105m-3. It is suggested that the terrestrial continuum may escape in bubbles of radiation enclosed by plasma downstream from the magnetotail.