Abstract: The invention relates to a method for the amplification of DNA and apparatus for such amplification. The method comprises steps typically found in amplification methods but utilises an optical procedure to detect denaturation of DNA or attainment of the desired denaturation temperature. The apparatus (1) comprises a temperature controllable chamber (2) including a rotor (3) for holding a plurality of reaction vessels (see 7 for example) for reaction mixtures including DNA, a drive means for the rotor, a heater (8) within the chamber for transiently supplying infrared energy to the reaction vessels, and an optical system (12-16) for determining denaturation of at least a reference DNA or for detecting attainment of a desired denaturation temperature in at least a reference reaction vessel.