Single or repeated sprays of up to 1,000 ppm ethephon ((2-chloroethyl)phosphonic acid) were applied to red raspberry (Rubus idaeus L. cv. Willamette) plants during the 1971, 1972 and 1973 harvest periods. Single ethephon sprays were followed by surges in fruit ripening, decreasing the total number of harvests required per season. The increased fruit ripeness corresponded to slightly decreased average fruit removal force among the fruit available for harvest. The enhancement of fruit ripening was greatest near the beginning of the harvest period. Repeated sprays did not improve the effects of ethephon, and both single and repeated sprays at concentrations from 250 to 1,000 ppm decreased the average fresh weight per berry by 10 to 15%. Fruit ripeness was also increased by extending the time between successive harvests from 3 to 5 days, but this was accompanied by increased fruit losses due to spontaneous fruit abscission during the interval between harvests. Repeated ethephon sprays in 1972 and 1973 did not increase the quantity of fruit recovered during mechanical harvests. It appears that the main potential for the use of ethephon in raspberry harvesting lies in its ability to control the timing and intensity of fruit ripening.