The invention relates to a method of determining the flow characteristics of a multiphase fluid along a flow path. The method involves applying a primary magnetic field to the flow of fluid in order to align the nuclei of the flow with the direction of this magnetic field, imparting a radio frequency on the flow in order to excite its nuclei and receiving a radio frequency emitted by the excited nuclei in order to obtain a Nuclear Magnetic Resonance (NMR) signal alternating between a phase ratio mode and a phase flow mode. The phase ratio mode involves processing the received radio frequency in order to determine the ratio of one phase with respect to another phase in the flow. The phase flow mode involves applying a secondary magnetic field in the region of the fluid flow which varies in magnitude along the length of the fluid flow path in order to provide a variation in the magnetic field experienced by the nuclei of the fluid flow dependent upon their position along the fluid flow path. This allows the velocity of the fluid flow to be calculated. Measurement apparatus for measuring the phase fraction and flow rate of phases present in fluid flow path is also provided.