The purpose of this study was to assess the prevalence of mental illness and to evaluate the quality of life of patients with neurocirculatory asthenia. A consecutive series of 80 patients who satisfied the diagnostic criteria developed by Kannel et al. for neurocirculatory asthenia was included in this study. Patients underwent a psychiatric diagnostic research interview and extensive psychometric evaluation, with both observer and self-rated scales for depression, anxiety, phobic symptoms, quality of life and abnormal illness behavior. In 47 patients (59%), a psychiatric diagnosis (mainly an anxiety disorder) antedated the onset of neurocirculatory asthenia, which was thus defined as secondary, also because cardiorespiratory symptoms were part of the mental symptoms. In the remaining 33 patients (41%) neurocirculatory asthenia was the primary disorder. Patients with secondary neurocirculatory asthenia reported significantly higher levels of anxiety, depression, social phobia, abnormal illness behavior and an impaired quality of life compared with patients with primary neurocirculatory asthenia. This latter did not significantly differ in these variables (except for depression) from healthy control subjects matched for sociodemographic variables. At a 1-year follow-up, patients with primary neurocirculatory asthenia had a much better prognosis than those with secondary neurocirculatory asthenia. The results indicate the feasibility of the primary/secondary distinction based on the time of onset of mental and cardiorespiratory symptoms in neurocirculatory asthenia. Since only about one quarter of the patients were found to suffer from decreased energy and fatigue according to specified criteria, the terms neurocirculatory asthenia and effort syndrome should probably be discarded.