Juvenile hormone-binding protein (JHBP) and the low-molecular-mass lipoprotein PBMHP-12 belong to a group of 30 kDa proteins that comprise the major protein component of the haemolymph specific to the fifth-instar larvae stage of the mulberry silkworm Bombyx mori L. Proteins from this group are often essential for the development of the insect. In a project aimed at crystallographic characterization of B. mori JHBP (BmJHBP), it was copurified together with PBMHP-12. Eventually, the two proteins were isolated and crystallized separately. The BmJHBP crystals were orthorhombic (space group C222(1)) and the PBMHP-12 crystals were triclinic. The crystals diffracted X-rays to 2.9 Å (BmJHBP) and 1.3 Å (PBMHP-12) resolution.