Results of an extensive study of the interfacial intermixing and interaction of the Pt/Ti bilayer metallization to seven III-V binary and related ternary compound semiconductor systems, as well as the contact electrical properties, are given. Pt/Ti contact to InAs and In0.53Ga0.47As were ohmic as-deposited, while the same metallization scheme on GaAs, GaP, InP, In0.52Al0.48As, and Ga0.7Al0.3As provided a rectifying contact as-deposited. The latter group of contacts, with the exception of InP and GaP, were transformed to an ohmic contact as a result of rapid thermal processing (RTP) at the temperature range of 300 to 450-degrees-C. A linear correlation between the semiconductor bandgap value and the Schottky-barrier height, measured in the Pt/Ti contacts, was observed.