As part of the Human Genome Variation Society (formerly known as the HUGO Mutation Database Initiative), a committee was formed to suggest standards for the description of sequence variants in DNA, RNA, and protein sequences. The committee proposed that the nomenclature should be unequivocal, precise, and short, and should prevent any possible confusion and follow existing practice as much as possible. To "spread the word," the nomenclature rules were published at regular intervals. This unit summarizes these nomenclature recommendations, which stimulated a uniform and unequivocal description of sequence variants in literature.