Abstract: The invention relates to a method for rapid detection of specific nucleic acid fragments with the aid of a PCR, consisting in amplifying target products in a special DNA thermocycler, provided with a special reaction thermal unit, which makes it possible to obtain, in reaction vessels in the form of standard polypropylene test tubes, a sloping temperature gradient directed at an angle to the direction of gravity. The amplification time is of 1-5 minutes. The inventive method can be recommended for DNA diagnostics, also field conditions, in medicine, veterinary sciences, in sanitary and epidemiological studies for detecting agents of dangerous infections, including potential bio-terrorist attacks, in criminalistics for identifying criminals in the food industry for detecting food products from genetically modified organisms, for testing raw material quality etc.