A method of performing a non-isothermal nucleic acid amplification reaction, the method comprising the steps of: (a) mixing a target sequence with one or more complementary single stranded primers in conditions which permit a hybridization event in which the primers hybridize to the target, which hybridization event, directly or indirectly, leads to the formation of a duplex structure comprising two nicking sites disposed at or near opposite ends of the duplex; and performing an amplification process by; (b) using a nicking enzyme to cause a nick at each of said nicking sites in the strands of the duplex; (c) using a polymerase to extend the nicked strands so as to form newly synthesized nucleic acid, which extension with the polymerase recreates nicking sites; (d) repeating steps (b) and (c) as desired so as to cause the production of multiple copies of the newly synthesized nucleic acid.