Crystals of methionine aminopeptidase from Escherichia coli have been obtained. The crystals are of space group P2(1) with unit cell dimensions a = 39.3 A, b = 62.6 A, c = 54.3 A, beta = 107.8 degrees and diffract to 2.1-A resolution. They contain one polypeptide chain in the asymmetric unit and are suitable for a high resolution crystallographic study.