To determine the adequate addition level of vitamin and mineral supplement to the ration for broiler chicks, 540 commercial broiler chicks were employed with six treatment groups such as 100%, 150%and 200% of NRC(1971) requirement level and 100%, 150%and 200% of Scott(1976) recommendation level. The results obtained during 8 weeks of feeding trial are summarized as follow: 1. Body weight gains and feed intakes of 200% NRC group and 100% Scott group were higher than those of other groups. In case of NRC groups, the growing performance was improved as the addition level of vitamin and mineral mixture was increased (p$lt;0.05). While, in case of Scott groups, no significant difference was found among the treatment level groups, but, conversely, slight and gradual decrease in body weight gain and feed intake were produced as the addition level was increased. 2. No significant difference in feed efficiency and nutrient utilizability was found among the treatment groups (p$lt;0.05). 3. Mortality and incidence of leg deformity were higher in 100% NRC requirement level than any other treatment groups, which did not show any marked differences among them. In conclusion, it seemed to be` apparent that miximum growing performance of broilers requires vitamins and trace elements equivalent to the level of 200% of NRC(1971) requirement or 100% of Scott(1976) recommendation level.