An octupolar crystal is produced from octupolar molecules of 1,3,5-tricyano-2,4,6-tris(p-diethylaminostyryl)- benzene and its structure is elucidated experimentally using the combined polarization analysis of two-photon fluorescence and second-harmonic generation (SHG). The optimal crystalline packing of the molecules in the crystal ( which originates from intermolecular pi-pi stacking interactions) -see Figure - results in a large SHG efficiency.