1. The ability to resist hypothermia was measured in 265 lambs of 10 breeds immersed in a progressively cooling water bath.
2. Cold resistance varied significantly between breeds, with hill lambs showing the highest resistance. Hill breeds and feral breeds together had the highest weight-specific cold resistance.
3. Cold resistance was positively correlated with birth weight and skinfold thickness.
4. Age at test varying from 1 to 60 h did not significantly affect cold resistance.
5. Rate of recovery from hypothermia varied slightly between breeds. The feral lambs tended to recover fastest.