Four rockets have been flown at Fort Churchill, Manitoba, to study the O2 (1Δg) concentration. Each rocket carried a single two-channel photometer sensitive to 1.27 μ radiation from the (1Δg → 3Σg−) (0,0) transition of O2. Information on the diurnal variation of both the total intensity and the height profile was obtained. The results agree with those reported by other observers and show the expected decay of the profile with increasing zenith angle. Some balloon-flight data are reported also.