1. Milk yields of grazing ewes with single lambs were estimated using two methods—the traditional lamb-suckling technique, and a technique involving hand-milking following stimulated let-down by intravenous injection of posterior pituitary gland extract (known as the oxytocin technique).

2. The oxytocin technique gave significantly higher figures for milk production than did the lamb-suckling technique (P < 0·01), and this persisted throughout lactation. Variation between ewes was similar for both techniques.

3. The two techniques are discussed in relation to the errors involved, and their accuracy and convenience of application to field conditions.

4. Differences in milk yield between Border Leicester x Merino ewes, and Romney Marsh x Merino ewes, estimated by either technique, were not significant. Correlation coefficients between lamb growth rate and milk yield of the ewe, measured by either technique, were high up to 7 weeks of age.

5. Where the ewes were under the same nutritional conditions before and after lambing, milk yield was not related to the live weight of the ewe, or birth weight of the lamb.