A technique in which an individual’s DNA is analysed to reveal the pattern of repetition of certain short nucleotide sequences, called short tandem repeats (STRs), throughout the genome. This pattern is claimed to be unique to the individual concerned, and the technique is therefore used for identification purposes in forensic science and paternity disputes, and in veterinary science. Sufficient DNA can be obtained from very small samples of body tissue, such as blood, semen, or hair. Usually a person’s DNA is analysed to reveal the length of STRs at each of certain genetic loci distributed on different chromosomes. For example, samples for the UK’s National DNA Database are based on analysis of a panel of 16 selected STR loci plus a gender identifier. The STR sequences are identified and amplified by the polymerase chain reaction using a commercially available kit, and the lengths of each sequence determined by a DNA sequencer and shown as an output trace of the fluorescence analyser. The results can then be compared with similar data stored on databases. See also microsatellite dna; randomly amplified polymorphic dna; variable number tandem repeats.