To date, only one sample from 1000 cubic meters of air at 88,000 feet has been obtained. Sampling was prevented by mechanical failures in two qther ascents. Sampling Results The results of atmospheric sampling to date are given in tabi ii. the four aircraftflights,| It will be noted that except for two of the concentrations reported are remarkably uniform, The value of 0.06 d/min/M? from the single 88,000 ft. sample compares favorably with the samples collected at roof level (mean 0.08 d/m/M?, range .OUu4.12 d/m/M3). Neglecting the two high values from the jet flights, the remaining tw average .07 d/min/W-’. samples