The thinning potential of various chemicals sprayed on `Tifblue' rabbiteye blueberry was examined in the greenhouse in 1990 and under field conditions in 1991 and 1992. In the greenhouse, BA concentrations ranging from 25 to 500 mg·liter -1 and carbaryl concentrations ranging from 400 to 2100 mg·liter -1 reduced fruit set when treatments were applied 16 days after corolla drop (ACD). GA 3 reduced fruit set only at 50 mg·liter -1 and NAA did not influence fruit set. In the field, BA at 75 mg·liter -1 and the combination of carbaryl at 400 mg·liter -1 and BA at 25 mg·liter -1 reduced fruit set in 1991 and 1992. Combinations of carbaryl and GA 3 reduced fruit set, but the response depended on GA 3 concentration and varied from year to year. GA 3 , NAA, and carbaryl also reduced fruit set, but the results were inconsistent. In 1991, greater thinning occurred when the treatments were sprayed 10 days ACD. BA at 25 mg·liter -1 increased fruit diameter at first harvest in 1991, and carbaryl at 400 mg·liter -1 increased fruit diameter in 1991 and 1992. Fruit diameter was increased in the presence and absence of thinning, depending on year and application time. Yield and return bloom were not influenced by any of the treatments. Chemical names used: 7 benzylamino purine (BA); gibberellic acid (GA 3 ); 2-naphaleneacetic acid (NAA); 1-naphthyl N -methylcarbamate (carbaryl).