A study was conducted to determine the effects of thinning and girdling at fruitset on growth, yield and fruit composition of Vitis vinifera L. cv. Ruby Seedless grapevines. Leaf water potential of girdled vines was higher than that of the control vines. Thinning resulted in an increase in shoot length and pruning weight. Berry weight was increased by 7 p. cent and 14 p. cent for the girdling and thinning treatments, respectively. The greatest berry weight (28 p. cent) occurred with a combinations of both treatments. Girdling significantly decreased titratable acidity and enhanced fruit coloration. Yield per vine was significantly decreased by severe thinning treatments. This study demonstrated that moderate thinning and girdling at fruitset could improve Ruby Seedless berry weight and composition without a severe decrease in yield per vine.