The relationship between canopy manipulation to improve solar penetration and ethephon application was studied on field-grown Vitis aestivalis L. `Norton' grapevines. Canopy manipulation involved removal of nonfruitful shoots, topping, and application of ethephon (750 mg·liter-1) at two intervals. Vines that were shoot-positioned and topped were not significantly different from control in soluble solids accumulation, but were superior to both ethephon treatments. Potassium levels in grape berries were lower in all treatments than in the control, but malate was significantly reduced only in the 2nd year of the 2-year study. Ethephon successfully controlled vine size and lateral development and thus increased solar penetration into the fruiting zone. Chemical name used: 2-chloroethyl phosphonic acid (ethephon).