The sphingolipids, such as cerebroside, sphingomyelin and mucolipid were isolated from rat brain, liver and kidney. The isolation of sphingosine bases from each sphingolipid was performed according to the method of Gayer and Sweely. The analysis of sphingosine bases was carried out according to the procedure of Sweely and Moscatelli, that is, by gas-liquid chromatography of long chain aldehydes obtained from sphingosine bases by periodate oxidation, and the results are summarized as follows. 1. Sphingosine bases are mainly consisted of C18-sphingosine (70-93%) and C18- dihydrosphingosine (4-15%) in all sphingolipids of rat tissues examined. But some quantitative differences in sphingosine base composition were observed between different sphingolipids and in lesser degree between a sort of sphingolipids in different tissues. 2. Brain mucolipid contained a substantial amount (23%) of C20-sphingosine and brain sphingomyelin also contained a small amount (3%), but no C20-sphingosine was detected in the sphingosine bases of brain cerebroside, brain sulfatide and all sphingolipids from other tissues. 3. There was a distinct tendency for more C18-dihydrosphingosine to occur in cerebroside than in sphingomyelin, which was seen not only in brain but also in other tissues. 4. Liver cerebroside contained 7.5% of phytosphingosine in addition to C,8-sphingosine and C18-dihydrosphingosine. Lesser amount of phytosphingosine was found in kidney cerebroside. The occurrence of phytosphingosine was further confirmed by thinlayer chromatography.