This publication summarizes the studies carried out at two of the most active volcanoes of Chiapas (Mexico): El Chichón and Tacaná. El Chichón erupted explosively in 1982 killing more than 2000 people being the worst volcanic disaster in Mexico, and Tacaná produced two mild phreatic explosions in 1950 and 1986. Only after these explosions a surge of new studies began to unreveal their volca…