In this paper we study the mod 2 cohomology ring of the Grasmannian Gn,3 of oriented 3-planes in R n . We determine the degrees of the indecomposable elements in the cohomology ring. We also obtain an almost complete description of the cohomology ring. This partial description allows us to provide lower and upper bounds on the cup length of Gn,3. As another application, we show that the upper characteristic rank of Gn,3 equals the characteristic rank of γn,3, the oriented tautological bundle over Gn,3.