Effects of lard, palm and rapeseed oil diets on the survival and fatty acid composition of liver and brain lipids were studied in male and female mice for 15 months. Over 80% of mice fed on lard and rapeseed oil (n-3 PUFA sufficient) diets survived to the end of feeding trial, however, 60% of male mice fed on palm oil (n-3 PUFA deficient) diet died before the end. Although a survival curve in female mice fed on palm oil diet was similar to that in male, it was not as dramatic as that of the male. The fatty acid analyses revealed that severe n-3 PUFA deficiency occurred in the mice fed on a palm oil diet. Moreover, the fatty acid was more deficient in the male than in the female. These results suggest that short life in mice may be caused by n-3 PUFA deficiency and, therefore, the fatty acid may be essential in enjoying a long life.