The low temperature deformation behaviour of austenitic high manganese alloys has been investigated. The total elongations of high manganese alloys (Fe-25Mn-5Al-5Ni-0.3C and Fe-30Mn-5Al-0.3C where the compositions are in weight per cent) increased with decreasing test temperature from room temperature (RT) to 77 K. This inverse elongation behaviour was attributed to the formation of strain-induced deformation twinning. On the contrary, the elongation of Fe-27Mn binary alloy goes through a maximum between RT and 77 K owing to the higher rate of strain-induced formation of epsilon-martensite. A new model for the calculation of uniform elongation has been proposed for the case in which a diffusionless transformation occurs with strain. This model has been applied to calculate uniform elongation, and the calculated values were in good agreement with measured values.