The study described in this article is concerned with the derivation of an average production function for 50 sheep farms on an area of light land in the Malvern County, Canterbury Plains, New Zealand. It is based on farm survey data for the 1955/6 season. The locality of the survey was chosen chiefly because it contained 51,000 acres of essentially similar soils, the Lismore series, and an adequate number of farms exhibiting a fairly high degree of homogeneity in their management. Although there are variations in farm management in the area, the predominant pattern consists of the maintenance of half bred, threequarter bred, or Romney-cross ewe flocks for the production of Downcross fat lambs. Most of the replacements for ewe flocks are purchased from other areas but some of the larger properties breed their own. The average winter carrying capacity of the sheep farms in the area was 1.7 ewe equivalents per acre for 1956. The system of farming is practically confined to a pastoral one due to the desiccating effect of the north west Fohn type winds which prevail during the summer. These conditions, combined with a shallow shingly soil, result in unreliable yields of cash crops and small seeds.