Effects of salinity stress at various fruit development stages from flowering to harvest on yield and fruit quality were investigated in single-truss tomato plants grown in hydroponics. Salinity stress was imposed by applying the concentrated drainage (EC 5.0 dS m^-1) instead of the standard solution (EC 1.2 dS m^-1) . Rates of water uptake and leaf photosynthesis were significantly inhibited by salinity at various growth stages. The earlier the salinity stress was applied, the lower the fruit weight and the higher the soluble solids content. Fruit fresh weight was severely decreased by salinity, whereas, fruit dry weight was less affected. When salinity was applied too early, there was a high rate of occurrence of blossom-end rot. Salinity stress beginning several days before harvest markedly prevented fruit cracking. From these results, we concluded that salinity was essentially a form of water stress, and that the resultant improvement of fruit quality and prevention of fruit cracking would be caused by the inhibition of water influx into the fruit. In single-truss tomato system, growers can easily produce various tomato fruit with different sizes and soluble solids contents by varying the time of application of the concentrated nutrient solution.