Low temperatures typical of early season production promote female sex expression and reduce male flower formation in summer squash. In addition, some summer squash cultivars do not produce sufficient male flowers for good fruit set early in the season in New York. Parthenocarpic fruit set could increase early season yield as well as at times when bee activity is restricted by wet weather or by row covers. More than 30 Cucurbita pepo cultivars and breeding lines were evaluated for their ability to produce parthenocarpic fruit over the past 3 years. Pistillate flowers were closed before anthesis to prevent pollination. In 1992, 66% of all the entries set parthenocarpic fruit where as 40% displayed the same pattern in 1993 and 81% in 1994. Varieties with the best parthenocarpic fruit set included Black Beauty, Black Magic, Black Jack, and Chefini Hybrid, all zucchini types. Most yellow-fruited cultivars had poor fruit set but the precocious yellow cultivar Gold Rush had good parthenocarpic fruit set in 1992 and 1993. In 1994, floating row covers placed over the plants 1 week after planting confirmed the results of the previous two seasons. This indicates that certain varieties of summer squash consistently set parthenocarpic fruit. These varieties may be most useful for early season production or for production under plastic tunnels or row covers where pollinator activity is restricted. In addition, our results indicate that it is possible to breed parthenocarpic squash of different fruit colors and types.