The optimisation of compressor stage aerofoil and fan blade design remains an important area of titanium alloy research and development for aerospace gas turbines. Such research has important implications for critical and sensitive component integrity and efficiency. In particular, a better understanding of how deformation twinning interacts with microstructural features in titanium alloys is required, because such twinning facilitates plastic deformation at a higher strain rate than dislocations. To investigate this behaviour commercial purity titanium was tested at room temperature and a high strain rate of 10³ s⁻¹ using ballistic impact testing. The results showed deformation twin interactions with various grain boundaries. There was evidence for the existence of Schmid-based twin type and variant selection for and deformation twinning modes in this material. The implications of the twin types observed and the interactions with grain boundaries are discussed. An absence of twinning also strengthens the argument that should not be considered a possible mode of deformation in titanium at room temperature and strain rates > 5 x 10² s⁻¹. New terminology is suggested for describing deformation twin and grain boundary interactions in α-phase titanium.