The results are presented of a study of the behaviour under uniaxial compression of absorption lines due to transitions from the ground state manifold of states of arsenic impurities in germanium to excited p states. It is found that the shear deformation potential constant Ell of the excited p states and conduction band minima of germanium is 16�4�0�2 eV. The equivalent deformation potential constant of the ground state, here designated as E~, is determined to be essentially the same (one analysis giving E~ = 16�5 � 0�4 e V), a result in contrast to that found for donors in silicon. The results are compared with those obtained by other workers who use a variety of techniques. Good agreement is found between the present results and a number of the others although several discrepancies remain.