The outer scale of turbulence L (0) has been calculated from values of the refractive-index structure coefficient C(2)(N) obtained from spatio-angular correlation measurements of stellar scintillation. It is found that L(0) </= 5 m for a large range of observations in France, U.S.A., and Chile and that its dependence on altitude Z follows the same general form at all these sites. The prediction of C(2)(N)(Z) profiles is shown to be feasible utilizing standard meteorological radiosonde data and this L(0)(Z) curve. A simple model based on dimensional analysis and a more complicated stochastic model are compared, but the latter appears to have no advantage.