Geranyllinalool, a polyisoprenoid compound, was found to block the early biosynthetic pathway of sphingolipids in LLC-PKl cells. Sphinganine, an intermediate in sphingolipid biosynthetic pathway, was abruptly accumulated in LLC-PKl cells at $2{;}{mu}M$ of fumonisin B1(FB1), a specific inhibitor of sphinganine N-acyltransferase, for 24 hr. Geranyllinalool lowered the $B_1(FB_1)$, a specific inhibitor of sphinganine N-acyltransferase, for 24 hr. Geranyllinalool lowered th FB1 and $50{;}mu$M geranyllinalool. l-Cy-closerine, an inhibitor of serine-palmitoyl transferase, was used as a positive control to evaluate the inhibitory effect of geranyllinalool. These results suggest that geranyllinalool may inhibit the serine-palmitoyl transferase, the first enzyme in de novo sphingolipid biosynthesis, resulting in the altered regulation of sphingolipid metabolism.