Cholesterol is very important for cellular membranes and ecdysteroids biosynthesis in insects. The sterol carrier protein SCP-x/SCP-2 has been speculated to have functions in intracellular movement of cholesterol and other lipids species. We have isolated the Manduca sexta sterol carrier protein x (MsSCP-x) cDNA. The MsSCP-x has a 3-ketoacyl CoA thiolase and SCP-2 domains. MsSCPx shares 80%, 79% and 64% similarity to Bombyx mori SCPx, Spodoptera littoralis SCPx and Aedes aegypti SCPx, respectively in the conserved domain.