Readily prepared copper nanoparticles were found to catalyse the 1,3-dipolar cycloaddition of azides and alkynes up to rates comparable to those of microwave chemistry. Both the preparation of the nanoparticles and the click reaction are carried out under mild conditions, in short reaction times and in the absence of any stabilising additive or ligand. A variety of 1,2,3-triazoles were prepared in