After a brief recall of the classical meaning of the concept of longevity, the first part of this chapter describes and summarises the main current technique for the estimation of age in reptiles. Among them, sclerochronology is primarily taken into account. The cautious analysis of seasonal growth cycles recorded in hard tissues, although not as rigorous as the mark-release-recapture method of animals in their natural conditions, now appears as a rapid and reliable chronological tool already successfully used in individuals of many reptile species. Sclerochronology is especially efficient for the comparison of several populations, and it is the only method for fossils. The second part presents a synthetic review of known longevities and records in the different groups of reptiles. A short discussion about the significance of longevity shows that for reptiles, because of their thermic metabolism (ectothermy), the physiological longevity must be strongly distinguished from the chronological longevity, especially for a comparison with that known for birds and most mammals.