Tomato aspermy virus (TAV) is a member of the T = 3 cucumovirus group, and the chrysanthemum strain (C-TAV) has been crystallized in a form suitable for X-ray structural analysis. The crystals, which grow in 14–17% ethanol at pH 8.5, are of orthorhombic space group I222 with unit cell dimensions of a = 295.1 Å, b = 320.5 Å, and c = 383.6 Å. There are two T = 3 virus particles in the unit cell, which means that they must be centered at 0,0,0 and 1/2, 1/2, 1/2 with icosahedral 222 symmetry elements coincident with crystallographic symmetry operators. The asymmetric unit of the crystals, therefore, contains one quarter of a virus particle, or 45 capsid subunits. Native diffraction data to 4 Å resolution have been collected using synchrotron radiation, though data appear to be present beyond that resolution. © 1995 Wiley-Liss, Inc.