Loop-mediated isothermal amplification (LAMP) is a novel nucleic acid amplification method that amplifies DNA with high specificity, efficiency and rapidity under isothermal conditions using a set of four specially designed primers and a DNA polymerase with strand displacement activity. We have developed a method that accelerates the LAMP reaction by using additional primers, termed loop primers. Loop primers hybridize to the stem-loops, except for the loops that are hybridized by the inner primers, and prime strand displacement DNA synthesis. Although both inner and loop primers react via the loops, they do so by different mechanisms. The LAMP method presented here uses loop primers to achieve reaction times of less than half that of the original LAMP method. Since the total time of analysis including detection is less than 1h, this new method should facilitate genetic analysis, including genetic diagnosis in the clinical laboratory.