PCR amplification has emerged as a very important tool in biological research. The utility of the PCR is, however, hampered by the fact that it is a slow technique. Faster heating cycles are therefore needed, both to enhance the activity of the enzyme, and to enable shortening of the reaction times. In this paper, polymerase chain reactions with focused microwave irradiation as the source of heat were demonstrated for the first time. Thus, it was established that continuous microwave heating does not terminate the enzymatic function of the polymerase. The results indicate the possibility to shorten the total reaction time. In addition, the technique may give the possibility to perform PCR reactions in millilitre scale.