Vanillyl-alcohol oxidase catalyses the oxidation of several 4-hydroxybenzyl alcohols by using 8-alpha-(N3-histidyl)-FAD as a covalently bound prosthetic group. Crystals of vanillyl-alcohol oxidase from Penicillium simplicissimum have been grown by using the vapor diffusion technique. The space group was found to be I, with cell dimensions a = b = 140.5 A, c = 132.9 A. Diffraction data have been recorded to 3.2 A resolution by using a laboratory source and to 2.5 A resolution on flash freezing the crystal at the ELETTRA Synchrotron X-ray diffraction beam line.