Abstract: This study was conducted to determine the parthenocarpic fruit set ability of some summer squash (Cucurbita pepo L.) cultivars (Eskenderany F1, Topkapı F1, Acceste F1, Sakız and Urfa Yerli). One day before anthesis, female flowers were clipsed and isolated with sellofan or pistil was plucked. Parthenocarpic response affected on cultivars, treatments, years and planting periods. Parhenocarpic fruit set ability of hybrid cultivars were more than open pollinated cultivars, Urfa Yerli wasn’t parthenocarpic fruit set but other cultivars varied in the amount of fruit set without pollination. Pistil plucked applications had more parthenocarpic fruit set than clipsed and isolated with sellofan applications. Parthenocarpic fruit set was high in 2001 for clipsed flowers but it was high in 2000 for pistil plucked flowers. First growing period was the best for pistil plucked flowers, but it was second period for clipsed and isolated flowers in both years.