This study was conducted in Department of Horticulture, Faculty of Agriculture, University of Cukurova in 1999 and 2000. Watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai] cultivar Crimson Tide was grafted onto 10 different rootstocks. Cucurbita moschata, Cucurbita maxima and Lagenaria siceraria were open pollinated cultivars, and Strong Tosa, Gold Tosa, P360 (Cucurbita maxima x Cucurbita moschata), Skopje, Emphasis, 216 and FRG ( Lagenaria spp.) were hybrid cultivars. The ungrafted Crimson Tide watermelon cultivar was used as the control. Plants were grown under low tunnel conditions until the outdoor temperature was suitable (22-25degreesC) for watermelon growth. Our results showed that while survival rate was low (65%) in Cucurbita type rootstocks, it was high (95%) in Lagenaria type rootstocks. Grafted plants flowered about 10 days earlier and showed more vigorous vegetative growth than the control plants. Grafted plants had up to 148% higher fresh weights than control plants. Similarly, grafted plants showed 42-180% higher dry weight, 58-100% more leaves and larger leaf area as compared with the control. In total yield, Lagenaria type rootstocks produced a higher yield but Cucurbita type rootstocks produced a lower yield than the control. While control plants had 6.43 kg/m(2) yield, Lagenaria type rootstocks produced 27-106% higher yield than the control. In contrast, Cucurbita type rootstocks had 127-240% less yield than the control. This could be attributed to incompatibility of Cucurbita rootstocks because some of the plants died before harvest. The study showed that rootstock choices influence plant growth as well as yield and quality of scion fruit, suggesting an important consideration in the potential use of grafting applications in watermelon.