The raising of fat lambs is not restricted to any particular system of farming, but limitations are imposed by many physical factors, the major ones being soil, climate, topography, and transport facilities. The aim of this investigation was directed towards obtaining information on; (a) the cost of producing rape, (b) the productive value or gross returns from rape as a fat lamb producer, and (c) the profit or loss on the rape crop when grazed by fattening lambs. The investigations reviewed the importance of rape as a fattening crop and the circumstances under which it is grown. It appears that rape will continue to be grown in the drier areas of the Dominion. It need not be considered essential in the maintenance of soil fertility, but it fits in well with the organisation of labour on cropping farms. The cost of growing the rape crop and the gross returns are influenced by numerous factors, many of which are outside the farmer’s control. The profit from the crop in those cases where store lambs are bought and fattened is governed mainly by the rape yield and the price of store lambs. Under average conditions for farmers to make a profit by buying store lambs and fattening them on rape, there is a tendency for the prices of store lambs to be too high. Finally, investigation has shown that the field to be covered is very complex, conditions varying with the efficiency of the farmer, with soil, weather, crop yield and breed of lamb as well as with the margin between store and fat lamb prices. Another factor, more difficult to measure, is the benefit obtained from rape in the general crop rotation and farm management.