Tyvelose (3,6-dideoxy-D-mannose or 3,6-dideoxy-D-arabinohexose) was found in hydrolysates of whole cells and native cell walls of Agromyces cerinus ssp. cerinus and some whole cell samples of Agromyces ramosus type strain (trace). The sugar was isolated, purified and identified by thin-layer and gas liquid chromatography, mass spectrometry, proton (H-1) and C-13 nuclear magnetic resonance' (NMR) spectroscopy as well as by optical spectrophotometry. Tyvelose was not found in the cell wall of other actinomycetes and Gram-positive bacteria tested so far.