This project was conducted at GAPEYAM, Sanhurfa, Turkey, in a semi arid region of Turkey. The aim was to determine the effects of water stress on 85 watermelon accessions collected from different regions of Turkey. Two irrigation levels were imposed to determine potential drought resistance of accessions. All plots in the beginning were irrigated with enough irrigation water for healthy seed germination. The plants received enough irrigation until the period of true leaves. After the true leaves, irrigation treatments were initiated. While S(1) treatment received full irrigation based on depleted soil moisture in the root zone, S(2) treatment received 50 % of S(1). A new formula was developed to evaluate the drought resistance. For each accession, the ratio between S(1) and S(2) treatments was calculated for each character: a ratio close to 1 indicated drought tolerance for this character. Both quality and physiologic/vegetative characteristics were measured such as leaf area, length of main stem, turgor pressure, last resistance test, diameter and weight of harvested fruits, total soluble solid contents, and number of seed and weight of seed. Drought tolerance of an accession was estimated by a linear combination of the ratio for these 9 traits. Accessions were classified as tolerant if they had a rating above 70 out of 100 and intolerant if the rating was below 59. The experimental results showed that thirty-five accessions were evaluated as drought tolerant. The highest score obtained from the formulae was 99 with accession number 24. Other tolerant accessions like 218, 25, 27 and 197 were rated as 88, 86, 86 and 85 respectively. Twenty-seven accessions were classified as intolerant.