3 Figs.]. The age distribution of four mole ( Talpa europaea Linnaeus, 1758) populations was determined by taking four direct measurements on the inner cusps, above the gum line, of the second upper molar teeth. At the end of the single annual breeding period, usually August, after babies were weaned, a mole population contained five age groups namely juveniles (approximately 4 months old) and adults in the approximate age categories in months: 16, 28, 40, 52. Only a small proportion of moles (6.6%) survived longer than 36 months. There was a preponderance of juveniles in all populations examined. The age distribution obtained by tooth measurements compared very favourably with that obtained by theoretical calculations. The age distribution of mole populations is affected by dispersal, previous trapping and drastic changes in weather and soil conditions which cause the death of moles. There were no sexual differences in the age distribution in the populations studied. The weight of the skull is not a reliable index of the age of moles in either sex but males have, on average, significantly heavier skulls than females. [Dept. Agric. Zool., School Agric., Univ. Edinburgh, Edinburgh EH9 3JG, Scotland]