The crystal structures of a complete series of configurational isomers of 2,3-epimino and 3,4-epimino derivatives of 1,6-anhydro-β-D-hexopyranoses were determined by single-crystal X-ray analysis. The structures exhibited conformational rigidity within the series regardless of the position and orientation of the aziridine ring. Possible formation of intramolecular hydrogen bonds involving the NH group is discussed with respect to the results of IR spectroscopy and to the intermolecular hydrogen bonds found in the crystal packing.