Polyamines are small organic molecules bearing two or more primary amine moieties. Biogenic polyamines such as spermidine, putrescine and spermine function as transcellular signaling molecules and are involved in diverse biological processes. Although small amounts of polyamines are synthesized in cells, larger quantities are often encountered as a result of putrefaction and decay, as they are the direct product of decarboxylation of amino acids such as methionine, lysine and arginine. The enzyme ornithine decarboxylase generates the polyamine putrescine, which is not only responsible for repulsive odor but is also implicated in cancer. Intracellular polyamines readily bind DNA and are critical to preventing oxidative DNA damage and directing DNA double-strand break repair pathways. Polyamine levels decline with age and dietary supplementation of the polyamine spermidine has recently been shown to reduce age-related oxidative stress and extend lifespan in mouse models of aging.