Ground based remote sensing measurements of sulphur dioxide column amounts made with the Brewer spectrophotometer have been used to estimate the total amount of sulphur dioxide injected into the stratosphere by the El Chichon eruptions which occurred between March 28 and April 4, 1982. Measurements were made at the Mauna Loa Observatory in Hawaii, at Toronto and on NASA Convair 990 flights between 20¿N and 50¿N. The average amount of sulphur dioxide measured at Mauna Loa was about 4.7 metmcm during late April and early May, 1982. The aircraft remote sensing measurements suggest that the cloud was distributed up to 35¿N in early May. Assuming that it was dispersed in a uniform belt around the globe between the equator and 35¿N, we estimate that 13.4 megatone of sulphur dioxide were injected into the stratosphere by the El Chichon eruptions. The amount of sulphur dioxide from the January ''mystery volcano'' was estimated to be 5.6 megatons. Previously, in 1980, an estimate of 0.6 megatons was made for the Mt. St. Helens eruption.