In an attempt to control fruit set and thereby increase fruit size, 2-(chloroethyl) phosphonic acid (ethephon), sodium 2,3-dichloroisobutyrate (DCIB), naphthaleueacetic acid (NAA) and N-dimethylaminosuccinamic acid (SADH) were applied as sprays to plants of the determinate tomato Lycopersicon esculentum Mill. ’Summit’ when fruit was set on six clusters. In comparison, one set of plants was deblossomed manually after the six-cluster stage, and another untreated. Although none of the chemicals provided perfect control of fruit load, NAA (100 ppm), SADH (4,000 ppm) + NAA (100 ppm), DCIB (4,000 ppm) + ethephon (500 ppm) and DCIB (6,000 ppm) were approximately 81, 77, 75 and 73% effective, respectively, in reducing fruit load. However, decreases in fruit load were not accompanied by corresponding increases in fruit size. In all probability, this was due to the impairment of normal growth by the chemicals. Several of the treatments produced substantial increases in early and total yield, by maturing a greater number of fruits and thus may be of potential use to commercial growers.