The tcm operon in Streptomyces glaucescens encodes a group of enzymes involved in the synthesis of the polyketide tetracenomycin (Tcm) C that exhibits both antitumor and antibiotic activities. Here, the crystallization and preliminary data characterization of the tcmG gene product, Tcm A2 oxygenase, which catalyzes the triple hydroxylation of Tcm A2 to form Tcm C, are reported. Tcm A2 oxygenase crystallizes in two different space groups, both with six monomers per asymmetric unit, resulting in large unit-cell parameters. Synchrotron data have been collected from both the hexagonal and tetragonal crystal forms to 4.5 and 4.2 A, respectively. The self-rotation function searches in both space groups suggest the monomers assemble into a complex with D(3) symmetry.