Medullary thyroid carcinoma (MTC) as a neuroendocrine tumour arising from C cells of the thyroid gland secrets hormonal peptides; among them, calcitonine (CT) and carcino-embryonic antigen (CEA). These two peptides are used for the diagnosis and treatment response of MTC cases. In patients with advanced MTC, scintigraphy by [(111)In-DTPA-d-phe1]-octreotide is able to detect somatostatin receptors (SSTR) and thus identify regional lymph nodes and/or distal metastases. In this article, we have studied the use of [(111)In-DTPA-d-phe1]-octreotide in the treatment of patients with advanced MTC, and a positive octreotide scan. Twenty-two patients were studied, 16 with persistent MTC and six with relapsed MTC. All patients' tumours were detected by [(111)In-DTPA-d-phe1]-octreotide-scan to be SSTR positive. All patients were treated with the somatostatin analog (SST-A) octreotide, for 3-21 months. Nine patients were treated only with SST-A (Group A). The remaining 13 patients (Group B) received adjuvant treatment as follows: six patients received chemotherapy (Ch), five patients received both Ch and external radiotherapy (eRT) and two patients received only eRT. Results were as follows: Group B patients as compared to Group A patients had about the same objective and biological response. Patients of Group B had relatively better subjective response (less diarrheas and abdominal cramps) versus Group A patients, although this finding was not significant. Group B patients had a longer mean survival time after treatment as compared to Group A patients: 39 months (with a range of 4-72 months) versus 20 months (with a range of 3-60 months) respectively, (P<0.05). Also Group B patients had longer than Group A patients mean total survival time - measured from the start of the disease: 138 (18-270) versus 97 (13-235) months respectively (P<0.05). Based on the above findings, it is the opinion of the authors that patients with advanced MTC and SSTR tumor expression in vivo as indicated by [(111)In-DTPA-d-phe1]-octreotide scanning, when submitted to treatment with SST-A octreotide and adjuvant Ch and/or eRT treatment may have a better treatment response than if submitted to treatment with SST-A octreotide alone. More cases are being studied by us at the present.