This feeding experiment was conducted to determine the nutritional requirements of the juvenile abalone (Haliotis discus hannai Ino ) for fa-t soluble vitamin D. The casein-gelatin-based diet containing seven graded levels of vitamin D was fed to the animals for 103 days. The red alga, Palmaria palmate, was used as a control diet . The results were summarized as follows: Moisture, lipid, protein content s of soft body and abalone growth were markedly af fected by the supplemental levels of dietary vitamin D, but the survival rate remained unaf fected. The progressive increase in alkaline phosphatase activity of the soft body reached a maximum value at an optimal dietary vitamin D level; however, excessive level of dietary vitamin D decreased its activity. Ash content, calcium and phosphorus composition of the shell were greatly affected by the vitamin D supplemented levels. Taking into considerat ion the weight, protein gain and alkaline phosphatase activity, it is proposed that the requirement of juvenile abalone for vitamin D is about 100IU per 100g diet.