The structural analysis of deacetylcephalothin [systematic name: (6R,7R)-3-hydroxymethyl-8-oxo-7-(2-thiophen-2-ylacetylamino)-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid], C(14)H(14)N(2)O(5)S(2), shows that the geometry of the central bicyclic moiety is close to the geometry exhibited by other biologically active cephalosporin antibiotics. The molecules are arranged in a helical chain running parallel to the 2(1) axis via a strong O-H...O hydrogen bond. The main helices are zipped together via N-H...O interactions, forming infinite layers. The supramolecular architecture is stabilized by O-H...S and C-H...O hydrogen bonds.