To search for the interaction of three antirachitogenic nutrients, calcium, phosphorus and vitamin D₃, two experiments were conducted using a total of 512 commercially hatched broiler chicks of Hisex Hybro strain. One experiment, arranged in 2 x 2 x 3 factorial design were used to study the growing performance of the chicks, supplemented with two levels (0.9, 0.45%) of calcium, two levels (0.7, 0.35%) of phosphorus and three levels (0, 200, 400 IU/㎏ diet) of vitamin D₃. Another experiment was designed to study the changes in serum calcium and phosphorus contents with or without vitamin D₃ dose. A 2 x 2 x 2 factorial arrangement with 4 replications of chicks was employed with two levels (0 and 0.66 g per day) of calcium, two levels (0 and 0.51 g per day) of phosphorus and two levels (0, and 30 IU per day) of vitamin D₃. The result obtained are summarized as follows. 1. There were significant effects on body weight gain with single administration of calcium, phosphorus and vitamin D₃ and also showed marked effects on growth rate with calcium x phosphorus interaction and calcium x vitamin D₃ interaction. However, present evidence indicated that the effect of phosphorus x vitamin D₃ interaction and calcium x phosphours x vitamin D₃ interaction on growing performance were not significant. 2. Feed intake were significantly (p $lt; 0.01) influenced by the single administration of calcium and vitamin D₃ and by the interaction of calcium x phosphorus, calcium x vitamin D, phosphorus x. vitamin D and calcium x phosphorus x vitamin D. There was not a significant effect of single phosphorus administration on feed intake. 3. It was found that feed conversion were also greatly influenced by the silagle supplementation of calcium, phosphorus and vitamin D₃. And also influenced by calcium x phosphorus, calcium vitamin D₃, phosphorus x vatimin D₃ and calcium x phosphorus x vitamin D₃ interaction. 4. Data revealed that there was no marked improvement in growing performance by in; creasing vitamin D₃ level to 400 IU/㎏ to the chicks, previously fed no or low vitamin D₃. But there was a great improvement on feed conversion with increasing level of vitamin D₃ to the chicks. 5. No significant differences were found in nutrient utilizabilities among treatments. Protein utilizabilities were gradually increased with increasing level of vitamin D₃ in optimum calcium fed groups and vice versa in low calcium received group. 6. Analytical indicated that raising the level of dietary vitamin D₃ led to increase in tibia ash content and calcium and phosphorus content of tibia. Tibia ash contents were greater in optimum calcium fed groups than in suboptimum calcium treated groups. However, there was no difference in tibia ash content between optimum and suboptimum phosphorus fed groups. 7. Supplementing no vitamin D₃ led to high mortality percent during experimentation. There was also significant difference in mortality between low and optimum calcium fed groups and not between dietary phosphorus level. 8. Present data showed that serum calcium level was, increased in contrast with the serum phosphorus level, decreased after vitamin D₃ administration. This tendency was evident at 12 hours after dose of vitamin D₃. When the optimum calcium was offered, the serum phosphorus contents was decreased after vitamin D₃ administration but showed no changes in no prior vitamin D₃ administration. It could be concluded that the supplementation of vitamin D₃ to the broiler chick diet is indispensable for the normal growth, especially in suboptimum level of calcium and phosphorus diet. It was also apparent that increasing vitamin D₃ above 200 IU per ㎏ diet did not show additional effect on the growing performance of chicks. It would be necessary to undertake more-detailed study for the time course information of serum calcium and phosphorus change after vitamin D₃ dose.