A two-dimensional dynamic model developed by Louis and Danielsen to study the global scale transport of tracers is applied to the investigation of the global scale dispersion of the eruption clouds of Volc¿n de Fuego (October 1974). Gunung Agung (March 1973), and Bezymianny (March 1956). The strength and chemical composition of source functions were adjusted so that the concentrations and concentration distributions agreed in general with actual measurements, published and unpublished. The resulting agreement with lidar measurements of the stratospheric aerosols is especially encouraging. The results indicate that the Fuego eruption injected no more than one fifth of the mass of material into the stratpsphere that was injected by the Agung eruption. Furthermore, an eruption of the size of that of Agung may inject into the stratosphere much greater amounts of chlorine in the form of hydrogen chloride than presently reaches the stratosphere annually as chlorofluoromethanes. As the model is applied to additional eruptions, the adjustments that must be made to the strength and chemical composition of the eruption cloud so that the model predictions agree with measurements of atmospheric trace constituents resulting from the eruption will furnish important information concerning the very early stages of the eruption cloud that to date has been very difficult to obtain.