The axial stiffness of single-lay cables composed of an arbitrary number of smooth wires is determined analytically from the general nonlinear theory for the bending and twisting of thin helical rods. Although large changes in the helix-angle are permitted, the longitudinal strain in each wire is assumed to be small. Numerical results are presented for two cases of practical interest, namely: (1)Cables with zero end-moment; and (2) cables restrained against end-rotation. It is found that the effective stiffness is strongly dependent upon the type of end-condition, except when the initial helix angle is close to 90—.