TIMETAL 555 (Ti-5Al-5Mo-5V-3Cr-0.6Fe) is a titanium alloy that can achieve property combinations potentially useful for structural applications. The alloy is currently under evaluation for several major airframe programs. A wide variety of strength, ductility and fracture toughness values can be achieved depending on thermomechanical processing and heat treatment. This presentation provides recent results regarding the interactions between heat treatment, microstructures and properties.