Quinohaemoprotein alcohol dehydrogenase from Comamonas testosteroni is a functional electron-transfer protein containing both a haem c and a pyrroloquinoline quinone cofactor. The enzyme has been crystallized at 277 K using polyethylene glycol 6000 as precipitant. The crystals belong to space group C2, with unit-cell parameters a = 98.1, b = 74.3, c = 92.2 A, beta = 105.9 degrees. A native data set with a resolution of 2.44 A resolution has been collected. The approximate orientation of the haem group with respect to the unit-cell axes has been determined from the optical properties of the crystals.