Sun photometer measurements of the spectral optical thickness of the El Chichon eruption cloud were obtained during an airborne latitudinal survey. The measured optical thicknesses were greatly enhanced over background levels for the stratosphere. The observations covered 44 ¿N to 36 ¿S, and increased optical thickness was found at all latitudes where measurements were made. Significant variations in the magnitude and spectral dependence of the optical thickness were found within the latitude range covered by the observations. The maximum optical thickness was found at 20 ¿N and the minimum was found at 30 ¿S. The optical thickness values ranged between 0.13 and 0.017 at 870 nm and between 0.15 and 0.044 at 440 nm.