1. From a screened cohort of 644 67-year-old men, drawn from the population of Gothenburg, 42 men with presumed cardiac dyspnoea were selected and compared with 45 random controls.
2. Cardiac function was evaluated by echocardiography and other non-invasive methods, and the potential of peripheral venous concentrations of immunoreactive atrial natriuretic peptide (IrANP), noradrenaline and adrenaline in revealing cardiac dysfunction was investigated.
3. Concentrations of venous IrANP and noradrenaline were both significantly, but weakly, related to the degree of dyspnoea and to pulmonary congestion.
4. IrANP, but not catecholamines, was also related to other indices of heart failure. The correlations were, however, due solely to increased immunoreactivity in men with severe dyspnoea; in most subjects with mild to moderate dyspnoea the level of IrANP was similar to that of the controls.
5. It is concluded that, in a population sample, the peripheral venous level of IrANP is more closely related to cardiac function than are catecholamines. Yet, the level of IrANP is not a very sensitive marker of cardiac dysfunction, suggesting that stimulation of α-human atrial natriuretic peptide release is a late phenomenon in the development of cardiac failure.