A coil arrangement for use in generating and detecting nuclear magnetic resonance (NMR) in a body, e.g. an NMR imaging apparatus, which comprises a conductor arrangement which can be used both as an RF field generating coil and an orthogonally polarised RF field detecting coil. The arrangement comprises a plurality of non-magnetic electrically conductive paths (34 to 50) extending generally parallel to the axis of a cylindrical volume, and means (51, 53) interconnecting the paths at each of their ends. An input signal applied to diametrically opposite paths (36 and 46) causes currents to flow in loops formed by the paths and interconnections so as to produce a field directed perpendicular to the axis of the volume, and an output for application to a detector is derived from diametrically opposite paths (31 and 41) which are orthogonal to the paths to which the input signal is applied so that zero current is induced in them by the field produced by the input signal.