Background/Aims: The plasma concentrations of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) become increased in hypertension. However, it is unknown what is the effect of the etiology and the severity of hypertension on the plasma concentrations of ANP and BNP. Methods: We examined plasma levels of ANP (measured as N-terminal fragment of proatrial natriuretic peptide; NT-proANP) and BNP in patients having sustained hypertension of different etiology and severity: in patients with renovascular hypertension (RVHT, n = 12), severe essential hypertension (SEHT, n = 37), and mild essential hypertension (MEHT, n = 29). In addition, we studied the diagnostic value of NT-proANP and BNP to discriminate patients with RVHT from patients with essential hypertension. Results: The plasma concentrations of NT-proANP and BNP were higher in the RVHT group (593 ± 80 and 25.0 ± 9.3 pmol/l, respectively) than in the SEHT group (320 ± 33 and 4.7 + 0.6 pmol/l, respectively; p < 0.001 for both), in spite of the similar blood pressure level, and also higher than in the MEHT group (356 ± 30 and 7.0 ± 1.0 pmol/l; p = 0.004 and p = 0.006, respectively). There was no difference in natriuretic peptide levels between the SEHT and MEHT groups. Plasma NT-proANP and BNP correlated positively with aging and serum creatinine concentration and inversely with left ventricular diastolic filling. In addition, NT-proANP correlated positively with systolic blood pressure and BNP with left ventricular mass index. The areas under receiver operating characteristic curves for plasma NT-proANP and BNP to discriminate RVHT patients from patients with essential hypertension were 0.793 and 0.782, respectively. The best cutoff value was 530 pmol/l for NT-proANP, giving a sensitivity of 67% with a specificity of 86%. The cutoff value of 9.8 pmol/l for BNP resulted in a sensitivity of 58% and a specificity of 90%. Conclusions: Patients with RVHT have higher plasma levels of NT-proANP and BNP than patients with essential hypertension. In addition to the etiology of hypertension, also left ventricular characteristics are important determinants of NT-proANP and BNP concentrations in hypertension. Due to the low sensitivity, NT-proANP and BNP are not suitable as screening tools for RVHT.