Hot PSC (channel-die) tests have been carried out to large strains (1.5) on 3 orientations of Al-1%Mn crystals, Bs{110}<112>, S{123}<412> and U{110}<110>, using a wide range of temperatures and strain rates (or Zener-Hollomon parameter Z). The deformation substructures are characterised by EBSD orientation mapping in terms of sub-grain sizes 6 and sub-grain misorientations and their frequency distributions over large areas. The sub-grain sizes respect the linear relation between 1/delta and lnZ but with significant orientation dependency. The largest sub-grains are found in the Bs orientation at all Z and the smallest in the S orientation at high strain rates. Sub-grain misorientations increase rapidly with strain to 3 or 4degrees then approximately stabilise after strains of 0.5 or 1. Some high angle boundaries (> 10degrees) are formed with frequencies about 10(-2) to 10(-3).