Experiments were conducted to determine the effect of diluted sea water on the germination of muskmelon seeds, the seedling growth, and the growth in sand and nutrient solution cultures. The germination rate was not significantly different from 0 to 5, 000ppm Cl and decreased at 6, 000ppm Cl 7 days after starting the germination test. Fresh weight of whole seedlings grown in sand for 16 days after germination decreased as sea water concentrations increasaed. Whole plant and fruit fresh weight in sand and nutrient solution cultures decreased with increasing sea water concentrations. The salt injury was observed at 250 to 1, 000ppm Cl in sand culture and at 3, 000 to 5, 000ppm Cl in nutrient solution culture. The degree of injury became more severe with increasing sea water concentrations. Osmotic potential of leaves, and transpiration rate and amount decreased as sea water concentrations increased. Root osmotic potential was higher than that of leaves. Content of Na in leaves and Cl in each plant part increased with increasing sea water concentrations. In nutrient solution culture the Na and Cl accumulated most in stem, followed by roots and fruit, and accumulated least in leaves. Na and Cl content in leaves was markedly high at 5, 000ppm Cl in nutrient solution culture because fruit did not set due to poor growth.