We characterize the spring and fall stratospheric distribution of CO at 49 ¿N--55 ¿S latitude from ATMOS profiles measured during 4 shuttle flights. Measured mixing ratios increase with potential temperature (&thgr;) from 12 ppbv (10-9 per unit volume) at 525 K, to 30--40 ppbv at 1750 K with only minor variations with latitude and season at a &thgr; level. Evidence for some confinement near 1150 K in the developing November 1994 vortex is indicated from comparison of CO and N2O horizontal gradients. Measured CO mixing ratios at the tropical tropopause are a factor of 10 higher than values calculated with a steadystate model using standard photochemistry constrained by correlative temperatures and pressures, and ATMOS measurements including CH4 as inputs. Differences decrease with latitude at constant &thgr; and are <20% at 800 K and all latitudes, where the CO photochemical lifetime is 40--50 days. ¿ 2000 American Geophysical Union