Method and apparatus for carrying out a thermal cycling reaction, wherein a succession of samples is conveyed through a series of sequentially arranged temperature control sites, each of the sites comprising means for supplying an electric current to, or inducing an electric current in, sample-containing vessels passing through it so as to induce temperature changes in the samples. Also provided is a sample support and its production, the support comprising a succession of sample vessels arranged sequentially one behind the next, preferably in the form of a linked chain, the support comprising an electrically conducting, preferably plastics, material which heats when an electric current passes through it.