Technical Abstract: Hormone induced spawning of channel catfish, Ictalurus punctatus, is the only reliable method to produce commercial quantities of channel catfish (female) x blue catfish, I. furcatus (male) hybrid. Channel catfish broodfish tend to mature over an extended period of time for optimal egg quality. Progression of oocyte diameter, plasma estrogen and testosterone, and vitellogenin profiles were monitored from November 2003 to May 2004 to stage the gonadal maturation in channel catfish. The ‘critical minimum’ diameter of oocyte to reach threshold maturity for 3-, 4- and 5- year old catfish was 2.0, 2.25 and 2.5 mm respectively. An increase in oocyte diameter at monthly intervals in 3 and 5-year old channel catfish mimicked the gonadal maturation (y=-3.158 +3.648x, r2=0.91, p<0.05; y=-3.22+3.22x, r2=0.69, p<0.05 respectively), but not in 4 year old catfish. The vitellogenin concentration in the blood plasma increased (p<0.05) at monthly intervals and with age of the fish also, vitellogenin concentrations for the combined group had a significant linear correlation (r2=0.66, p<0.001, n=18) with mean oocyte diameters. Findings suggest oocyte diameter and plasma vitellogenin can be used as predictive factors to determine and stage development of the gonads and anticipate imminence of spawning.