During a series of lactation studies on ewes a half-udder technique was used for comparing twice- with thrice-a-day milking. The treatments were applied to the half-udders of 8 ewes in a Latin square design, in which each period lasted 7 days. Essentially the treatments were as follows: (A) a half-udder milked twice daily whilst the opposite half-udder was milked thrice; (B) a half-udder milked thrice daily whilst the opposite half-udder was also milked thrice; (C) a half-udder milked twice daily whilst the opposite half-udder was also milked twice.