Electron transfer from p-InP photocathodes to competing electron accepters, oxidized metallocenes, and dibromoethylbenzene (DBEB), in acetonitrile solutions was investigated in order to access the Limitations associated with detecting hot electrons in such systems. Low and highly doped p-InP electrodes were investigated under various illumination conditions and acceptor concentrations. Collection experiments showed that the fraction of photocurrent which reduced DBEB decreased from one to zero as oxidized metallocene, decamethylferrocenium(+) (DFER+) or dicarbomethoxycobaltocenium (DCMC+), was added to a DBEB solution. Mott-Schottky data revealed a corresponding decrease in the negative shift of the bandedges under illumination which went to zero at the same metallocene concentrations at which DBEB reduction was no longer detected. Voltammograms revealed hysteretic double waves in cases where the metallocene was not present in large enough concentrations to accept all electrons. The data indicate that the rate constants for reduction of DFER+ or DCMC+ by conduction-band Electrons are at least two orders of magnitude larger than for reduction of DBEB. Although previous research on these interfaces was interpreted as evidence for reduction of DBEB by hot electrons at highly doped p-InP electrodes, these results indicate that it would be difficult to distinguish between hot and thermalized photoreduction mechanisms in these systems.