"Multi-composite wire" is a new type of strong wire for winding coils to generate very strong-pulsed magnetic fields. The basic concept is filling the free spaces in a bundle of thin conducting wires with reinforcing fibres, and enclosing this composite wire in an insulating sleeve. In this concept, any desired combination of conductor and reinforcement can be used. To insulate the wire and keep the bundle together, a sleeve consisting of a strong insulating fibre is braided around the core. As a proof of principle, multi-composite wires have been made consisting of soft copper in combination with carbon fibres. Glass fibre was employed for the sleeve. The mechanical properties of the wires were determined from tensile and "explo-vessel" tests. The latter allows the investigation of the mechanical properties under conditions as they prevail in a coil. The first experimental wire had up to 88% of the theoretically calculated UTS. Further development is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.