An umbilical for use in the offshore production of hydrocarbons, and in particular to a power umbilical for use in deep water applications is described, comprising a plurality of longitudinal strength members, wherein at least one longitudinal strength member comprises rope enclosed within a tube. In this way, the or each longitudinal strength member being a rope and tube combination achieves the synergistic benefit of favorable mechanical properties in the axial direction, with favorable mechanical properties in the radial direction during tensioning or the like of the umbilical, especially during installation.