Vacuum ultraviolet photoelectron (PE) spectra of InxPx- (x = 2-13) clusters were measured to probe the evolution of their electronic structure with size. The spectra of smaller (x less than or equal to 6) clusters show numerous discrete electronic features, with fewer seen for x = 7 and 8. For x greater than or equal to 9, the PE spectra comprise two broad peaks resembling the first two valence bands of the InP bulk photoemission spectrum and calculated density of states. Electronic structure calculations show that the character of the electronic states contributing to the two bands in the cluster PE spectra is similar to that in the bulk photoemission spectrum. (C) 2004 Elsevier B.V. All rights reserved.