We have examined the absolute yield of keV x-rays emitted from gaseous plasmas created by the intense irradiation of large Xe clusters. We find that>10 &mgr;Jof x rays with photon energies above 1 keV are produced from clustering Xe gas targets when heated by 250 mJ, 2 ps laser pulses at an intensity of∼1017 W/cm2.The yields show strong laser intensity dependence and variation with Xe cluster size. ©1997 American Institute of Physics.