In this study an attempt was made to provide controlled empirical evidence for the hypothesis that chronic idiopathic pain might be a specific form of ‘masked depression’. For this purpose, chronic pain patients supposed to be suffering from a ‘masked depression’ were compared to patients with organic pain and coexistent depression, patients with only organic pain, and patients with only depression, in a double-blind placebo-controlled therapeutic trial with mianserin. Although mianserin appeared to have effective antidepressant properties in this study, no pain improvement was found in any of the three chronic pain groups. These results challenge the validity and clinical relevance of the ‘masked depression’ concept for chronic idiopathic pain.