Millions of mice are used annually in research and teaching. The exact relationship between age of the animals compared with the age of humans is still subject to discussion and controversy. Literature review analyzing the age of rats in comparison with men age. Were reviewed the existing publications on the subject contained in Medline / PUBMED, SciELO, The Cochrane Database of Systematic Reviews and Lilacs crossing the headings rats, experimental surgery and physiology. Rats rapidly develop during childhood and become sexually mature at about six weeks old, but reach social maturity five to six months later. In adulthood, every month of the animal is approximately equivalent to 2.5 human years. Several authors performed experimental studies in rats and estimated 30 days of human life for every day life of the animal. The differences in anatomy, physiology, development and biological phenomena must be taken into consideration when analyzing the results of any research in rats when age is a crucial factor. Special care is necessary to be taken when the intention is to produce correlation with human life. For this, special attention is needed to verify the phase in days of the animal and its correlation with age in years of humans.
