We developed a new time-resolved immunofluorometric assay (TR-IFMA) using two monoclonal antibodies for the total renin measurement in human plasma and follicular fluid. No conversion of prorenin to renin was needed because the assay detected both renin and prorenin. The detection limit of the assay was 10 ng/L and the linear range was 10-25,000 ng/L. Within-assay precision (CV) was 15-8% at renin concentrations of 50-12,200 ng/L. Between-assay precision was 19-3% at concentrations of 100-18,000 ng/L. Analytical recovery of added renin was 85-104% (n = 5) in plasma samples and 104-119% (n = 3) in follicular fluids. For plasma, the reference interval was 78-262 ng/L in men (n = 44) and 36-226 ng/L in women (n = 43).