Abstract: The effects of drip irrigation application amounts on watermelon (Citrullus vulgaris, c.v. Crimson Sweet) were evaluated under Thrace conditions. Irrigation amount treatments ranged from zero to 100 % of soil water replenishment in 25 % increments for whole growing season. Treatment T1 in which irrigation water was adequately applied during the total growing season required 116.02 mm, 186.88 mm and 293.81 mm of irrigation water in 1998, 1999 and 2000, respectively. The seasonal evapotranspiration and total yield at this treatment were determined as 362.13 mm and 103.69 t/ha in 1998, 400.02 mm and 89.84 t/ha in 1999, 408.03 mm and 75.42 t/ha in 2000, respectively. For each differential water treatment, the parameters of fruit morphology (size, height and rind thickness), total soluble solids, total sugar, pH and total yield were analyzed. As a result it was found that yield and some yield components such as fruit height, rind thickness were affected by irrigation water amounts. But treatments had little or no effect on fruit size, total soluble solids, total sugar and pH. Irrigation water use efficiency (IWUE) and water use efficiency ranged from 24.31 to 197.89 kg/da-mm and 17.17 to 30.30 kg/da-mm, respectively.