2-Ammo-3-hydroxyhex-4-ynolc acid, reported previously from Tncholomopsu rut~lans, was shown to be a nuxture of its three- and erythro-forms They were separated from each other and characterized by elementary analysis, optical rotation, TLC, IR, NMR spectra, catalytic hydrogenation, and by chenucal synthesis Their configuratlons were determmed by the comparison of then hydrogenation products with known three- and eryrhro-2-ammo-3-hydroxyhexanoic acids