​Samples representing the various lithological types present in different volcanic units from the S, Miguel island (Azores) were collected during a preliminary survey carried out in this island, Both the results obtained by multivariate analysis and the study of the behaviour of incompatible and compatible trace elements on the volcanic rocks from S. Miguel reveal that they were derived from two distinct magma types: a trachytic magma (evolving at shallow magma chambers) and a basaltic magma. Differences in the evolutionary path followed by the two liquids are thought to be responsible for the petrographical and chemical diversity displayed by all the volcanic units of S. Miguel with the exception of the Picos Complex. Geophysical observations support the existence of magma chambers, probably filled with trachytic magmain the upper part, underlying the Furnas, Fogo and Sete Cidades volcanoes. Although the Picos Complex is the most recent, the geophysical data shows no evidence of the presence of a subjacent magma chamber, which may explain the absence of trachytic rocks within this Complex. Therefore, this area of the S. Miguel island may have formed under a distinctive tectonic setting and, deserves particular attention in future work.