Large-scale field trials in sugar beet were undertaken between 1961 and 1963 to examine the effects of chemical or mechanical weed control followed by machine thinning in terms of labour economy and yield of the crop. The seedling populations were left untrimmed by hand and, where the weed-control measures were completely effective or nearly so, the crops were left unweeded. Yield samples were taken both by hand and by machine so that the potential yield as well as the likely commercial yield might be determined. The chemical and mechanical methods that were studied saved about 75% of the normal labour demand and gave root yields 91.5% of those following hand work.