Superplastic forming (SPF) properties of TIMETAL54M (Ti-5Al-4V-0.6Mo-0.4Fe, or Ti-54M) sheet were investigated. A total elongation of Ti-54M exceeds 500% at temperatures between 750°C and 850°C at a strain rate of 10-3/S. Values of strain rate sensitivity (m-value) measured by jump strain rate tests are 0.45 ~0.6 in a temperature range of 730°C to 900°C at a strain arte of 5 x 10-4/S or 1 x 10-4/S. Flow stress of the alloy is 20 ~ 40% lower than that of Ti-6Al-4V (Ti-64) mill annealed sheet. The observation of microstructure after the tests revealed the indication of grain boundary sliding in a wide range of temperatures and strain rates.