1. The behaviour of dairy cattle under normal commercial conditions of management was studied in two series of observations:

(a) Four cows were observed continuously for 24 hr. on four occasions at approximately two-weekly intervals.

(b) A herd (average fifty-two cows) was observed continuously for 24 hr. on twelve occasions at approximately monthly intervals.

2. Under our conditions and within our definitions, the cows grazed 6–52 hr., lay down 9–22 hr. and loafed 8–26 hr. on an average during 24 hr.

3. The cows ruminated 5–60 hr. per 24 hr.; 4–52 hr. when lying down and 1–08 hr. when loafing.

4. On average the animals defaecated 1T6 times, urinated 9–8 times, and drank 3–8 times in 24 hr.

5. One animal walked an average distance of 1–74 miles per 24 hr., excluding journeys to the cowshed.

6. No aspect of grazing behaviour was found to be strongly related to either current milk yields or air temperature.

7. When on ‘good’ pasture, as compared to ‘poor’, the animals grazed for a shorter time, walked less, and took fewer drinks.

8. From the results of the herd observations a similar periodicity of behaviour during 24 hr. was observed throughout the year but was more apparent when environmental conditions were similar.

9. When the herd was confined to 5 ft. concrete standings during the winter nights, the animals did not rest as comfortably as when out of doors.

10. Major peaks of grazing or eating were recorded after each milking followed by periods of lying down, especially during the night.

11. Time of sunset has been related to the time when grazing ceased and the herd lay down.

12. In view of the data collected, tentative suggestions for improving grazing management are made.