The review is devoted to loop-mediated isothermal amplification (LAMP) – a novel molecular diagnostic method that has recently become increasingly popular. Unlike polymerase chain reaction, LAMP does not require thermal cycling; DNA or RNA amplification occurs at a constant temperature (about 65 °C) with 4 or 6 primers. This is a fast, highly-sensitive, and highly specific method, which does not require expensive equipment, where visual detection of the reaction products is performed by the unaided eye. LAMP is successfully used for the diagnosis of multiple viruses, bacteria, and other pathogens (including those in food). Moreover, it can be applied for the detection of singlenucleotide polymorphisms. Recently, a modified LAMP assay – one-step nucleic acid amplification (OSNA) – was validated for metastasis detection. OSNA was demonstrated to have almost the same sensitivity and specificity as standard diagnostic methods (sometimes even higher). Particular attention is paid to the mechanism of LAMP, primer design, and diagnostics of cancer using OSNA.