An essentially new application of chronoamperometry is presented for the determination of homogeneous second-order rate constants for the reactions between small molecule reductants and redox proteins. The first part of the work is a comparison between stopped-flow kinetics and chronoamperometric kinetics for the reaction of ferrous-EDTA with horse cytochrome c. The reaction was demonstrated to be first order in both ferrous-EDTA and cytochrome c and the effect of ionic strength was also studied. All of the chronoamperometric results compared well with the stoppedflow work which had been done previously. Chronoamperometry was then used to study several other reactions which have not been previously examined, including the reaction of ferrous-diethylenetriamine pentaacetic acid with cytochrome c. The reaction was slower than the ferrous-EDTA reaction but was more sensitive to ionic strength because of the greater charge (-3) on the complex. The second study was the reaction of ferrous-EDTA with Rhodospirillum rubrum cytochrome cz as a function of ionic strength. This novel application of chronoamperometry to small molecule-redox protein reactions represent a new and relatively easy alternative to anaerobic stoppedflow kinetics.