Extensive experience from patients with gastrinoma as part of the multiple endocrine neoplasia type 1 (MEN 1) syndrome has revealed that MEN 1-gastrinoma patients show important differences from patients with sporadic gastrinoma. These differences comprise clinical, pathological and biochemical features, but are especially pertinent to the therapeutic approach. Therefore, the diagnosis of the MEN 1 syndrome is of great clinical importance to the gastrinoma patient and his family.