Circulating immunoreactive atrial natriuretic peptide, IrANP(99-126) and the N-terminal fragment of the prohormone, IrANP(1-98) were measured in two population samples from the general population of Gothenburg, Sweden. A group of 85-year olds (974 subjects) and a group of 40-year olds (191 subjects) were investigated in respect of cardiovascular, renal and metabolic disease. IrANP(99-126) and IrANP(1-98) were significantly higher in the 85-year olds compared to the 40-year olds, and were significantly increased in subjects with congestive heart failure, ischaemic heart disease, atrial fibrillation and renal dysfunction but not in subjects with hypertension. Eighty-five-year-old subjects who were on treatment with digitalis, beta-adrenergic-blockers, nitrates and diuretics had significantly increased IrANP(99-126) and IrANP(1-98). In multivariate analysis IrANP(99-126) concentrations were predictive for congestive heart failure, ischaemic heart disease, atrial fibrillation and treatment with beta-blockers and anti-depressant drugs. IrANP(1-98) was predictive for congestive heart failure, ischaemic heart disease, atrial fibrillation, diabetes mellitus, renal failure and drug treatment with beta-blockers and neuroleptics. We conclude that measurements of circulating concentrations of IrANP(99-126) and/or IrANP(1-98) may add valuable information in the diagnosis of congestive heart failure and ischaemic heart disease in an elderly population. It remains to be determined whether routine measurements of circulating IrANP (99-126) and IrANP(1-98) may be of value in predicting current cardiovascular disease for the individual patient.