Isolated reaction centers from Rhodopseudomonas viridis contain two high-potential c-type cytochromes, cytochrome c-559 and cytochrome c-556, and two low potential c-type cytochromes, cytochrome c-552 and cytochrome c-554. At moderate redox potentials, the two low-potential cytochromes are oxidized and are not identifiably involved in light-induced turnover. Following a flash, in the absence of functional secondary acceptor quinone, Q B, the charge separation states, C + H2C H1Q − A and C + H2C + H1Q − A are rapidly created, where C H1 is cytochrome c-559 and C H2 is cytochrome c-556. Decay of these two states occurs via slow intramolecular charge recombinations. The rates of recombination for the two states were distinguishable and were pH and temperature dependent. At pH 9 and 296 K, k app H1 = 8.5 ± 0.5 s −1 for the charge recombination of C + H2C + H1Q − A and k app H2 = 0.95 ± 0.05 s −1 for the charge recombination of C + H2C H1Q − A. It was suggested that the mechanism for decay of both cytochrome c +Q − A states is via repopulation of the P +Q − A state, where P is the primary donor, followed by rapid (ms) recombination of this state, with a rate k P. Recovery of C + H2C H1Q − A also requires thermal equilibrium between the two hemes: C + H2C H1 a3 C H2C + H1. In addition to these indirect paths, there is a direct route of recovery for each of the states, C + H2C H1Q − A and C + H2C + H1Q − A. The direct pathways are evident at low temperature when the recovery processes become almost temperature independent, below about 220 K. In 60% ethylene glycol, the limiting rates are: k 0 H1 = 1.85 s − for C + H2C + H1Q − A, and k 0 H2 = 0.15 s −1 for C + H2C H1Q − A. That these rates differ by only a factor of 10 is remarkable in view of the 30 Å (center-to-center) separation between the two high-potential hemes and the involvement of intermediate states is briefly considered. From the model, the calculated rates, at any temperature, are given by: k app H1 = (k P + K c k 0 H1 ) (1 + K c ) for C + H2C + H1Q − A recombination, and k app H2 = [k P + K c (k 0 H1 + K e k 0 H2 )] [1 + K c (1 + K e )] for C + H2C H1Q − A recombination, where K c is the equilibrium constant for the positive hole to lie on either P or C H1, and K e is the equilibrium constant for electron transfer between the two high-potential cytochromes, C H1 and C H2. Equilibrium redox titrations distinguished the two high-potential cytochromes c and revealed their distinct pH and temperature dependences. K c was taken from the difference in the measured equilibrium midpoint potentials ( ΔE m) of the C + H1/C H1 and P +/P couples, and K e was taken from ΔE m for C + H2/C H2 and C + H1/C H1. The rate of P +Q − A decay, k P, was taken from measurements when all c-type cytochromes were chemically oxidized, and this was used to approximate the rate when the high-potential cytochromes were reduced. All three variable parameters were measured over a range of pH and temperature, and the calculated rates were compared to experimental rates determined under these conditions. The agreement between calculated and measured values was good and provides strong support for the proposed mechanism. The adequacy of equilibrium E m values and the measured value of k P is discussed in terms of possible electrostatic interactions between charged redox centers. It is concluded that such interactions are of minor importance for all relevant parameters in isolated reaction centers.