Calculations have been performed to determine the rate coefficients of several reactions involved in both the formation and depletion of interstellar HCO+ and HOC+. The abundance of HOC+ deduced from these calculations is consistent with the tentative identification of HOC+ in Sgr B2 by Woods et al. The large HCO+/HOC+ abundance ratio observed by Woods et al. is due at least in part to a more rapid formation rate for HCO+ and probably due as well as to a more rapid depletion rate for HOC+.