Abstract: An inductive fluid heater is constructed from two concentric tubular members forming a fluid chamber therebetween. Fluid is supplied into the chamber by way of a manifold at each end of the concentric tubular members. A heating device is located within the chamber where the heating device is in the form of a shorted secondary coil of a transformer. The shorted secondary coil is in the form of a conductive tube. The transformer further includes a primary coil, a central core and a plurality of side cores to form a continuous constrained flux path. The central core surrounded by the primary coil is inserted into the inner concentric tubular member of the fluid heater. The primary coil may be powered by an AC high frequency supplier. Potential applications include fluid heating in general, particularly medical applications where blood, plasma and the like are required to be heated at high flows rates and under highly controlled conditions.