This study was carried out using rats weighing $40{sim}50;g$ which were devided into seven groups with various diet compositions emphasizing fat levels of perilla seed oil for the period of 41/2 weeks. The levels of fat in the diet were 5%, 10%, 15% and animals were fed ad libitum. The results are as follows : 1) Yellow pjgmentation of both neck and tail was clearly observed in groups fed 10% and 15% level perilla seed oil without vitamin I supplementation (IV and VII). 2) The growth rate in groups fed 15% level perilla seed oil was reduced as compared to that in groups fed 5% or 10% level perilla seed oil. 3) The mean hematocrit values of 15% level perilla seed oil groups tended to be lower than those of control group, tut the differences were not significant. 4) The serum vitamin I concentration showed different value in various groups, the values of control group were significantly higher than those of perilla seed oil groups-15% level with or without vitamin E supplementation (VI and VII) and 10% level without vitamin E supplementation (IV). According to the results, 10% level-perilla seed oil in the diet can be considered safe if vitamin E is not omitted from the vitamin mixture ana the group fed 15% fat with P/S ratio of 1 appeared to be safe during the experimental period. Finally the long-term studios have to be persued in many aspects by using perilla seed oil in the experimental diet. Because rats are known t4 be quite resistant to the experimental diets, comparative studies using various animal species have to he conducted.