We have previously described that the N-glycosylation process was accompanied by the release of oligosaccharide-phosphates and neutral oligosaccharides. The relationship between oligosaccharide-P-P-dolichol and its metabolic products (glycoproteins, oligosaccharide—phosphates and neutral oligosaccharides) was investigated by analysing the structure of the oligosaccharide moieties and the kinetic behaviour of the various species in pulse and pulse/chase experiments. For these studies, a glycosylation mutant of Chinese hamster ovary cells (B3F7) which does not synthesize mannosylphosphoryldolichol was utilized. Evidence was obtained for the presence of two pools of oligosaccharide-P-P-dolichol which have different fates. One pool is not glucosylated, is rapidly labelled and immediately chased by mannose, and generates the oligosaccharide—phosphate species. The second pool is glucosylated, exhibits a lag time (5–10 min) prior to being labelled, and is utilized in the glycosylation of proteins and in the production of neutral oligosaccharides. We postulate that the cleavage of non-glucosylated lipid intermediates generating oligosaccharide—phosphates represents a ‘bypass’ in the dolichol cycle which allows direct regeneration of dolichyl phosphate. The other metabolic fate of non-glucosylated oligosaccharide—lipids, glucosylation, results in their use as effective substrates for the glycosylation of proteins or in the generation of neutral oligosaccharides.