Vocal communication and consequent recognition between ewes and their own lambs or alien lambs was investigated by recording the bleating of one ewe and one lamb separated by a canvas barrier. Border Leicester, Dalesbred, Jacob and Soay, ewes were tested once when their lambs were 20-27 days and once when they were 70-80 days old. The number of bleats made by ewes and lambs over 3 min. was recorded, and the number of times they answered each others bleats within 2 sec. of hearing the first bleat, was calculated. Both ewes and lambs bleated more and answered more bleats when they were bleating to own rather than alien animals. Vocalisations were less with older lambs, particularly in the Soay sheep. The Dalesbred ewes answered significantly more of their own lambs' bleats than alien lambs, compared with other breeds. The Dalesbred lambs answered more of their own ewes' bleats when they were 70-78 days old. It is concluded that this vocal behaviour of answering bleats may help the lambs to identify their ewes more easily.