1. Forty Greyface (Border Leicester ♂ × Blackface ♀) and 40 North Country Cheviot ewes, due to lamb to a Suffolk ram in April 1969, were housed during December 1968 in eight groups of 10 ewes, the breeds being penned separately.

2. One pen of each breed received a basal diet of either hay, grass silage or arable silage with a ‘high’ level of concentrate supplementation and one pen of each breed was given hay with a ‘low’ level of concentrate supplementation. Within each pen, five of the 10 ewes were clipped at housing and the other five were clipped in the following June.

3. Voluntary intakes of the basal diets declined with advancing stage of pregnancy, particularly for those receiving grass silage. Feed had no differential effects on the performance of the ewes in terms of wool yield, body-weight change, birth weight of lamb per ewe or perinatal lamb mortality.

4. The Greyfaces clipped at housing yielded less wool than those Greyfaces clipped in the following June. Time of clipping had no influence on the wool yield of the Cheviots. Wool grades were not affected by time of clipping. Ewes clipped in December performed significantly better than ewes not clipped until June with a higher proportion of ewes producing multiple births (P<0·1), a higher total birth weight of lamb per ewe (P<0·01) and a reduced perinatal mortality of the lambs (P<0·05). The total effect of this improved performance was that the clipped ewes produced 53 ·5 % more live lambs than those ewes not clipped until the following June.