Differential SO2 column measurements of the Mt. Pinatubo volcanic plume were made from a NASA Electra aircraft flying in the Caribbean in July, 1991. The mean column content of the volcanic plume in the Caribbean was 25 &mgr;atm m (2.5 Dobson units) with periods of over 100 &mgr;atm m observed. The data indicate that an aerosol absorption or scattering effect occurs for long slant paths (low sun elevation angles) and 41 &mgr;atm m (an average obtained for 1-2 airmasses) may be more representative of a true column average. Dispersion of the initial cloud from Mt. Pinatubo and a one month SO2 to sulfate conversion time constant are in good agreement with the column contents found here. ¿American Geophysical Union 1992