Gastrointestinal stromal tumors (GIST) are rare mesenchymal neoplasms of the gastrointestinal tract with a malignant potential and unpredictable behavior. In the literature a few cases of synchronous development of a GIST and another neoplasia with different incidence, etiology, evolution and prognostic have been described. We report a case of a 61 year old male with a simultaneous occurrence of a GIST and a colon adenocarcinoma.