A novel human Glyco_18 domain-containing protein, SI-CLP, was detected recently in human bronchoalveolar lavage of patients with chronic inflammatory disorders of the respiratory tract and peripheral-blood leukocytes. The expression of SI-CLP is up-regulated by dexamethasone or IL-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 A. The crystals belong to the space group P3(2)21 with unit cell parameters a=b=99.79 A, c=250.53 A, alpha=beta=90 degrees, gamma=120 degrees. There are two molecules per asymmetry unit.