Disintegrins are low molecular weight proteins (4-15 kDa) with an RGD binding region at their binding loop. Disintegrin and disintegrin-like proteins are found in the venom of four families of snakes: Atractaspididae, Elapidae, Viperidae and Colubridae. This report describes the biological activity of a disintegrin, crotatroxin 2, isolated by a three-step chromatography procedure from the venom of the Western diamondback rattlesnake (Crotalus atrox). The intact molecular mass for crotatroxin 2 was 7.384 kDa and 71 amino acids. Crotatroxin 2 inhibited human whole blood platelet aggregation with an IC50 of 17.5 nM, inhibited cell (66.3p) migration by 63%, and inhibited experimental lung tumor colonization in BALB/c mice at 1000 μg/kg. Our data suggest that while crotatroxin 2 inhibits platelet aggregation, cancer cell migration, and lung tumor colonization it is done via different integrinsResearch Group (CBRG), Department of Chemistry, Texas A&M University-Kingsville, FONACIT (G-2005000400), Caracas,Venezuela, and grant # CA098056 (MAM), University of Delaware.