alpha-Methylacyl-CoA racemase is a key enzyme in the metabolism of 2-methyl-branched fatty acids and, in mammals, in the conversion of cholesterol to bile acids. The enzyme from Mycobacterium tuberculosis has been purified to homogeneity and crystallized by the hanging-drop vapour-diffusion method. The crystals of the unliganded racemase belong to space group P6(1)22 or P6(5)22, with unit-cell parameters a = b = 122.0, c = 256.4 A. Data sets were collected at 100 K. The crystals diffract to 2.8 A using synchrotron radiation.