Galectins are generally believed to be potential candidates for use in the development of novel antiinflammatory agents or as selective modulators of the immune response. In particular, galectin-9 exhibits some of the extracellular functions, including cell aggregation, adhesion, chemoattraction, activation, and apoptosis. Tl-galectin (Tl-gal, galectin-9 homologue gene) was isolated from an adult worm of the Toxascaris leonina. The full-length Tl-gal gene, which was incorporated into pET-28a, was overexpressed in E. coli and purified by nickel affinity and gel filtration chromatographies. The purified Tl-gal was crystallized using the hangingdrop vapor-diffusion method. The crystal belonged to the tetragonal space group $P4_1$, with unit-cell parameters of a = b = $75.7AA$ and c = $248.4AA$. The crystals were obtained at $20^{circ}C$ and diffracted to a resolution of $3.0AA$. The asymmetric unit contained four molecules of Tl-gal, which gave a crystal volume per protein mass (Vm) of $2.8AA^3Da^{-1}$ and a solvent content of 54.1%.