A photoinitiated O2(1/1)-EI-N2 mixture has been made to lase with an output energy of over 160mJ. The utilization efficiency of the stored Oa(1) energy attains 12%. A comparison between O2C(1)-CHsI-Nj mixture and Oa(1)-CFal-N2 mixture suggests that the former exceeds the latter in many respects. It is also shown that Na is as good a buffer gas as AT in the oxygen-iodine laser with respect to the laser output.