In the present paper the authors present some data on the geology of Santos considering particularly the occurrences of basic rocks. The geologic map shows the main occurrences of these rocks, indicating their respective geologic coordinates. A rather detailed petrographic study of rocks, sampled at the occurences of São Vicente and ilha Porchat, revealed that the first one was a lam prophyric dike with a high percentage of olivine whereas the rock of the ilha Porchat was classified as diabase. It is the opinion of the authors that these occurrences originated at different geologic times, and that the olivinic rocks of São Vicente, whose origin is likely to be connected with the epeirogenic movem ents of the serra do mar, are younger than the diabase of the ilha Porchat