Pig heart carbonyl reductase (PHCR), which belongs to the short-chain dehydrogenase/reductase (SDR) family, has been crystallized by the hanging-drop vapour-diffusion method. Two crystal forms (I and II) have been obtained in the presence of NADPH. Form I crystals belong to the tetragonal space group P4(2), with unit-cell parameters a = b = 109.61, c = 94.31 A, and diffract to 1.5 A resolution. Form II crystals belong to the tetragonal space group P4(1)2(1)2, with unit-cell parameters a = b = 120.10, c = 147.00 A, and diffract to 2.2 A resolution. Both crystal forms are suitable for X-ray structure analysis at high resolution.