1The internal growth rings of the teeth of the crabeater seal (Lobodon carcinophagus) are described and the annual pattern established. 2By examination of near term foetuses, recently weaned pups, half‐year‐old, one‐year‐old and older animals the probable pattern of dentine deposition in the first year is established. The neonatal line is conspicuous; a line marking the time of weaning is present and also a line which probably represents the pup moult. The rate of dentine deposition is discussed and it is suggested that lactation extends over about five weeks. 3Using ages determined from the growth rings in the canine teeth, an average growth curve for body length has been constructed and is compared with earlier estimates of the rate of growth in the first few years. 4Evidence is given which suggests that the average neonatal length is 45 in. The sizes subsequently attained by the two sexes are similar, though the largest females tend to be slightly larger than the largest males. The mean body length of animals over twelve years old is 89 $2–36 in. 5The question of the age at sexual maturity is re‐examined and it is concluded that in the female sexual maturity is usually attained at an age of a few months over two years. 6The age distribution of the two samples of crabeater seals is discussed. The oldest animals in the material were 19 years old on the basis of dentine rings.