Biological data support the development of clinical trials designed to evaluate the activity of somatostatin (SMS) analogues in advanced breast cancer (ABC). Although previous clinical trials have failed to show antitumor activity, various factors may have biased their results. In an attempt to improve our understanding of the role of SMS analogues in ABC, 10 patients with favourable prognostic factors and who had not been heavily pretreated for advanced disease were treated with lanreotide 30 mg i.m. fortnightly (depot formulation). Blood samples were periodically taken to evaluate the effect of the drug on growth hormone (GH) and insulin-like growth factor 1 (IGF-1) and to determine drug serum levels. Although the drug was well tolerated, no clinical activity was observed. Serum GH and IGF-1 levels were not properly suppressed over time and drug serum concentrations fluctuated widely. In conclusion, SMS analogues cannot be recommended even as palliative treatment of ABC. Further studies should be undertaken to investigate the effect of higher drug doses, given subcutaneously or by means of continuous infusion, in suppressing GH and IGF-1 serum levels.