Juvenile hormone-binding protein (JHBP) isolated from Galleria mellonella haemolymph has been crystallized using the hanging-drop method in two polymorphic forms. The best diffracting crystals (2.7 A) are trigonal, space group P3(1)21 (or P3(2)21), with unit-cell parameters a = 110.4, c = 93.9 A. X-ray diffraction data have been collected for the native crystals using synchrotron radiation and cryogenic conditions (100 K).