Fruit size of peaches is an important quality factor that can be optimized by adjusting the number of fruit on the tree by hand thinning 40 - 60 days after full bloom (dafb). Hand thinning is labor intensive and therefore the development of other strategies to reduce production cost is warranted. Since ethylene plays a key role in peach fruitlet abscission, it is hypothesized that foliar applications of ethephon will induce fruit abscission and increase fruit size. Ethephon (0 to 400 mg·L–1) was applied to “Redhaven” peach trees 45 - 50 days after full bloom in 2005 and 2007 to determine the efficacy and concentration required to induce fruit abscission. Abscission was linearly related to ethephon concentration and as a result reduced fruit set by 70% to 100 %. These data indicate that ethephon in the range of 100 - 200 mg·L–1 can be used to induce adequate levels of fruit abscission of ‘Redhaven’ peaches without inducing trunk or limb gummosis.