Mustang is an algorithm to align multiple protein structures. Given a set of PDB files, the program uses the spatial information in the Calpha atoms of the set to produce a sequence alignment. Based on a progressive pairwise heuristic the algorithm then proceeds through a number of refinement passes. Mustang reports the multiple sequence alignment and the corresponding superposition of structures. . When using this program please cite A.S. Konagurthu, J.C. Whisstock, P.J. Stuckey, A.M. Lesk, "MUSTANG: A multiple structural alignment algorithm." Proteins: Structure, Function, and Bioinformatics. 64(3):559-574.