A novel human Glyco-18 domain-containing protein, SI-CLP, was detected recently in human bronchoalveo-lar lavage of patients with chronic inflammatory disorders of the respiratory tract and peripheral-blood leukocytes. The expression of Sl-CLP is up-regulated by dexamethasone or 1L-4 and involved in the Th2 cell pathway. To further investigate its structure and function will provide new insights into human immunity and related disorders. Here we provide a preliminary crystal image of SI-CLP using the hanging-drop vapor diffusion method. The crystals of SI-CLP diffracted X-rays to a resolution of 2.7 Å. The crystals belong to the space group P3221 with unit cell parameters a = b =99.79 Å, c =250.53 Å, α=β=90°, γ=120°There are two molecules per asymmetry unit. © 2009 Bentham Science Publishers Ltd.