The high temperature deformation behaviour of cast and homogenised near α titanium alloy Titan 29A (M/s MIDHANI, India), equivalent to IMI 834 (M/s TIMET, UK) was studied towards developing a processing map. The processing map is interpreted in terms of the microstructural changes occurring during deformation, based on the values of a dimensionless parameter η which represents the energy dissipation through microstructural evolution processes. An instability criterion (ξ < 0) is applied to demarcate the flow instability regions in the processing map. Both the parameters (η and ξ) were computed from the experimental data generated by hot isothermal compression tests conducted at various temperature (T) and strain rate (έ) combinations T = 850-1100 °C and έ = 3 × 10−4 to 10 0/s. The deterministic domains observed in the investigated temperature and strain rate regime are attributed to continuous dynamic recrystallization of α lamella and dynamic recrystallization of β grains. © 2013, Springer-Verlag France.