Monthly dispersion patterns of vertically rising balloons for various probability levels are computed for the altitude of 90,000 ft by using the effective vertically integrated standard deviation of the wind. These are representative of conditions at the Holloman AFB - White Sands Missile Range complex. The use of this procedure to obtain a reliable measure of dispersion is verified by testing with individually computed ascent trajectories. The importance of considering interlevel correlation coefficients in estimating dispersion is emphasized by the results of this study. The resulting dispersion patterns afford a means of increasing balloon operational efficiency and effectiveness for the cited area by defining the best locations for target flight launchings, and by giving the probable dispersions for flights launched from a fixed site. The findings of this study can also be of assistance in planning balloon operations at other midlatitude locations. (Author).