LCI is a type of novel antibacterial polypeptide secreted by a Bacillus subtilis strain. It consists of 47 residues with a molecular weight of 5468 Da. Using bioengineering, LCI was expressed in Escherichia coli DH5 with recombinant plasmid pBVAB16. It was crystallized using PEG 4000 as a precipitant. The crystal belongs to space group P6 2 22 or P6 4 22, with unit-cell parameters a = b = 29.30, c = 187.09 A Ê , and diffracts to 2.44 A Ê . A set of diffraction data to 2.8 A Ê was collected.