Coachella Valley Thompson Seedless grape growers have been applying a gibberellin spray to the fruit soon after bloom to increase berry size. Test plot work in previous years has shown that a variation of timing of this application by as little as a week can produce important effects on berry size, fruit maturity, shape of the berry, and density of the cluster. Better results have been obtained with two applications than were achieved with only one. Such tests in previous years have been made on commercial vineyards where the grower thinned and girdled at the time he thought best. This study was conducted to evaluate the effect of the timing of any one of these operations upon the results obtained from any other.