This work was carried out during two seasons of 1997 and 1998 to study the effect of cluster thinning on yield, fruit quality and storage life of Ruby seedless grapes. Cluster thinning were performed after fruit set, using removal about 0, 15, 30 and 45% of cluster number combined with removal a last quarter of the cluster to reached about 18-20 cm length per cluster and thinning of berries were performed when berries size reached about 8 mm. This study revealed that cluster thinning treatments used decreased the yield, shot berries percentage in cluster and acidity in berry juice than the untreated thinning. Increasing cluster removal percentage resulted in increased individual berry weight and size, juice volume, dry matter percentage in berries, T.S.S. content and total anthocyanin in berries skin. Moreover, decreased percentage of shatter, decay, loss in weight and total loss percentage had obtained during storage life than the control.