In the present study, we have investigated the liver microsomal stearic acid delta9 desaturation, and the fatty acid composition of liver microsomal total lipids in 10- and 30-day-old spontaneously hypertensive rats (SHRs), compared to the normotensive Wistar Kyoto (WKY) control rats. So as to avoid any influence related to the diet, the composition of the milk being different in SHR and WKY strains, the pups were suckled by adoptive normotensive female Wistar. After weaning, the 30-day-old rats were fed a standard commercial diet and then killed. Our results show lower liver microsomal delta9 desaturase activities in the 10- and 30-day-old SHR versus the WKY of the same age. The fatty acid composition of the SHR liver microsomal total lipids are not in agreement with the changes in the delta9 desaturase activities at the two studied ages. This phenomenon depends not only on desaturation/elongation but also on other interacting aspects of lipid metabolism including oxidation, substrate availability, acyl exchange, and eicosanoid synthesis, as well as hormonal status.