The first measurements of high-energy x-ray emission ($h\ensuremath{\nu}\ensuremath{\sim}30\ensuremath{-}300$ keV) by high-$Z$ microballoon targets irradiated at $5\ifmmode\times\else\texttimes\fi{}{10}^{14}l\ensuremath{\phi}l2\ifmmode\times\else\texttimes\fi{}{10}^{16}$ W/${\mathrm{cm}}^{2}$ by 10.6-\ensuremath{\mu}m laser light are reported. An exponential spectrum with a slope $k{T}_{H}\ensuremath{\sim}250$ keV provides the best fit to spectrometer data at ${\ensuremath{\phi}}_{l}={10}^{16}$ W/${\mathrm{cm}}^{2}$. The hard-x-ray yield indicates that a substantial fraction, probably between 10% and 100%, of the absorbed laser energy is converted to hot electrons. The slope $k{T}_{H}$ is proportional to the fastest ion energy.