The (pro)renin receptor ((P)RR) is expressed in several tissues including kidney, heart and brain, and is thought to regulate the tissue renin-angiotensin system (RAS) through the non-proteolytic activation of prorenin. (P)RR is cleaved by furin to generate soluble (P)RR (s(P)RR), which is secreted into the extracellular space. s(P)RR is a candidate biomarker reflecting the status of the tissue RAS. Here, we investigated the relationship between background factors and serum s(P)RR levels. We measured s(P)RR levels in 122 patients with essential hypertension (EH) and assessed the relationships between background factors and s(P)RR levels. Serum s(P)RR levels were 19.0±4.9 ng ml(-1). Single regression analyses showed that age (r=0.251, P<0.01), serum creatinine levels (r=0.229, P<0.05) and urinary angiotensinogen excretion (r=0.196, P<0.05) were positively correlated with s(P)RR levels, whereas estimated glomerular filtration rate (eGFR; r=-0.337, P<0.001) were negatively correlated. Multiple regression analyses of age, blood pressure (BP), hemoglobin A1c (HbA1c) and s(P)RR levels revealed that age and s(P)RR levels were negatively correlated with the eGFR (P<0.05). In patients with EH, serum s(P)RR levels correlated positively with renal function independent of age, BP and HbA1c. These findings support s(P)RR as a useful biomarker that reflects the status of the tissue RAS.