The tail tag and the tagging method are described. A total of 711 harp and hooded seals have been tagged in the years 1951-1963. Excepting experimental tagging of one adult and 18 immature harp seals in the Barents Sea in 1963, all seals have been tagged as pups, at Newfoundland in 1951-1952, in the Jan Mayen area in 1951-1963, and in the Barents Sea in 1963. Of the tagged seals, 54 have been recaptured within the first six weeks after tagging. Early recoveries in 1953 and 1955 illustrate the dispersion of weaned harp seal pups in the Jan Mayen area. Recoveries after one or more years amount to 14, and most of these are from the tagging areas. One recovery indicates a connection between hooded seals breeding at Newfoundland and the moulting hoods in the Denmark Strait. One other recovery suggests some contact between the Jan Mayen and the White Sea harp seal populations. Recaptures of one harp and one hooded seal have provisionally verified the ageing method bascd on dentine growth zones for these species. Finally, some factors that may influence the number of recoveries are discussed, and means of improving the tagging method are suggested.