To get insight into the selective etching of In0.53Ga0.37As and In(0.72)G(0.28)As(0.61)P(0.39) with respect to InP in alkaline K3Fe(CN)(6)-containing solutions, the electrochemical and etching properties of Zn0.53Ga0.47As and In0.72Ga0.28As0.61P0.39 were studied by rotating (ring)-disk voltammetry and by electrical impedance and etch rate measurements. It is shown that both In0.53Ga0.47As and In0.72Ga0.28As0.61P0.39 are etched by K3Fe(CN)(6) in an electroless etching process, in which holes are injected by K3Fe(CN)(6) and consumed in the anodic dissolution. The observed selectivity in the etching of In0.53Ga0.47As and In0.72Ga0.28As0.61P0.39 vs. InP is due to a difference in valence band-edge position, which determines the hole injection rate. Furthermore, it was found that a mechanism of galvanic element formation enhances the selectivity when InP and In(0.53)G(0.47)As or InP and In0.72Ga0.28As0.61P0.39 are in electrical contact.