Abstract: This paper presents a general kinematical analysis for nonproportionaldouble slip in fcc and bcc crystals. The analytical formulas for the deformation gradient arc obtained for bilinear path double slip and piece-wise proportional double slip. The purely kinematical equation for the tangent vector of a line element is derived.The axis rotations on a stereographic projection are illustrated for several different slip-system combinations, initial axis positions in both fcc and bcc crystal.An accurate numerica...