Abstract A comparison has been made of the enzymes catalyzing the transfer of manose, glucose and N-acetylglucosamine from, respectively, GDPmannose, UDP-glucose and UDP- N-acetylglucosamine to endogenous dolichol phosphate (Dol- P) in liver Golgi membranes. Evidence is presented which suggests that all three reactions utilize the same pool of Dol- P. The transfer of mannose from GDP-Man to Dol- P is not inhibited by 0.1 mM UDP or UMP; 0.1 mM GDP did block the accumulation of mannose in Dol- P-Man. The net transfer of glucose and N-acetylglucosamine to Dol- P is prevented by 0.1 mM UDP but not 0.1 mM GDP. UDPglucose inhibits the reverse of the glucose transfer reaction but not reverse of the N-acetylglucosamine or mannose transfer reaction. On the basis of this, and other data, it is concluded that the three sugar transfer reactions utilize separate enzymes.