1. Foot-and-mouth disease broke out on three pig farms of the Spetchley area of Worcestershire after the virus had been carried to them in skimmed milk.

2. A study of the natural features of the area and of the climatic conditions during the outbreak show that the wind could have carried the virus from one or other of these three to twenty-six others of the total thirty-two farms infected.

3. Bringing the cattle from the fields and keeping them in their sheds offered no protection. Nine farmers did so but the only effect was that the onset of infection was delayed for a day or so.

4. The direction in which cow-sheds faced likewise made no difference. Openings in the walls for ventilation obviously allowed virus to be carried inside.

Mr J. S. Needham, M.R.C.V.S., first showed me that the wind could have been responsible for the spread of the disease in the Spetchley outbreak. I am glad to be able, after my study, to support his view. I am indebted to Mr V. Harris, Officer-in-charge, R.A.F. Meteorological Station, Pershore, Worcestershire, for the climatic details.