Aerosol optical thicknesses were derived from solar spectral extinction measurements. These were made with a sunphotometer on board the NASA Convair 990 aircraft during May, July and December 1982 over a range of latitudes covered by the flight mission. Large increase in the optical thicknesses over the background levels for the stratosphere were found at all latitudes where observations were made; these are attributed to the El Chichon eruption cloud. The latitudinal variation of the optical thickness in May and July shows a maximum in the vicinity of the eruption, a minimum near 30¿N and no appreciable change further north of the minimum. This is indicative of a thick portion of the cloud being confined between 0¿ and 30¿N latitude. In December, the maximum was fond near 8¿N, the minimum near 25¿N and an increase north of the minimum. The spectral dependence of the aerosol optical thickness which is different on one side of the 30¿N latitude from the other suggests that the two portions of the cloud have different size distributions of aerosols.