A molecular fragment comprising the first two domains of the human vascular cell adhesion molecule-1 (VCAM-1) has been crystallized by the vapor diffusion method. Two crystal forms have been examined by X-ray analysis: One crystal form belongs to the space group C2 with two molecules in the asymmetric unit and cell parameters: a = 122.1 A, b = 48.9 A, c = 73.4 A, and beta = 117.4 degrees. The other crystal form belongs to the space group P2(1) with one molecule in the asymmetric unit and cell parameters: a = 40.4 A, b = 45.7 A, c = 54.7 A, and beta = 100.5 degrees. Diffraction data up to 1.9 A resolution have been collected for the C2 crystal form.