ABSTRACT Background Following nephrectomy, the remaining kidney tissue adapts by an increase in glomerular filtration rate (GFR). In rats, hyperfiltration can be transferred by plasma. We examined whether natriuretic peptides, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) increase in plasma proportionally with kidney mass reduction and, if so, whether the increase relates to an increase in GFR. Methods Patients (n = 54) undergoing partial or total unilateral nephrectomy at two Danish centres were followed for 1 year in an observational study. Glomerular filtration rate was measured before, and 3 and 12 months after surgery. Natriuretic propeptides (proANP and proBNP) and aldosterone were measured in plasma before and at 24 h, 5 days, 21 days, 3 months and 12 months. Cyclic guanosine monophosphate (cGMP) was determined in urine. Results There was no baseline difference in GFR between total and partial nephrectomy (90.1 mL/min/1.73 m2 ± 14.6 versus 82.9 ± 18; P = 0.16). Single-kidney GFR increased after 3 and 12 months (12.0 and 11.9 mL/min/1.73 m2, +23.3%). There was no change in measured GFR 3 and 12 months after partial nephrectomy. ProANP and proBNP increased 3-fold 24 h after surgery and returned to baseline after 5 days. The magnitude of acute proANP and proBNP increases did not relate to kidney mass removed. ProANP, not proBNP, increased 12 months after nephrectomy. Plasma aldosterone and urine cGMP did not change. Urine albumin/creatinine ratio increased transiently after partial nephrectomy. Blood pressure was similar between the groups. Conclusion ANP and BNP increase acutely in plasma with no relation to degree of kidney tissue ablation. After 1 year, only unilateral nephrectomy patients displayed increased plasma ANP, which could support adaptation.