A double-antibody radioimmunoassay for human follicle-stimulating hormone (FSH) and human luteinizing hormone (LH) which can be carried to completion in 48 hours was compared with the conventional six-day double-antibody radioimmunoassay. The bound-over total (B/T) dose response curves for the 48 hour assay were comparable in slope and dose range with the six-day assay and the four per cent average within-assay and the nine per cent between-assay coefficients of variation for the 48 hour assay were comparable with the variation observed in the conventional six-day assay. Maximum variation among identical serum samples assayed in both systems was 15.3 per cent so that quantitative results obtained with either assay system were comparable.