Calf pancreas microsomes incubated with UDP-N-acetyl-D-[14C] glucosamine in the presence of Mn2+ incorporated radioactivity into P1-2-acetamido-2-deoxy-D-glucopyranosyl P2-dolichyl pyrophosphate and P1-di-N-acetyl-alpha-chitobiosyl P2-dolichyl pyrophosphate. The formation of both glycolipids was enhanced to the same extent by exogenous dolichyl phosphate. Labeled P1-di-N-acetyl-alpha-chitobiosyl P2-dolichyl pyrophosphate was formed from synthetic P1-2-acetamido-2-deoxy-alpha-D-glucopyranosyl P2-dolichyl pyrophosphate and from prelabeled pancreatic P1-2-acetamido-2-deoxy-alpha-D-glucopyranosyl P2-dolichyl pyrophosphate without the addition of divalent cation. Upon thin layer chromatography, it had the same mobility as synthetic P1-di-N-acetyl-alpha-chitobiosyl P2-dolichyl pyrophosphate recently synthesized by Warren et al. (Warren, C. D., Herscovics, A., and Jeanloz, R. W. (1977) Carbohydr. Res., in press), but was different from the synthetic compound prepared by Wedgwood et al. (Wedgwood, J. F., Warren, C. D., Jeanloz, R. W., and Strominger, J. L. (1974) Proc. Natl. Acad. Sci. U. S. A. 71, 5022-5026).