This report provides an updated user's manual for DYNA3D, an explicit three-dimensional finite element code for analyzing the large deformation response of inelastic solids and structures. A contact-impact algorithm permits gaps and sliding along material interfaces with friction. Using a specialization of this algorithm, such interfaces can be rigidly tied to admit variable zoning without the need of transition regions. Spatial discretization is achieved by the use of 8-node solid elements, 2-node beam elements, 4-node shell elements, 8-node solid shell elements, and rigid bodies. The equations-of-motion are integrated in time by the central difference method. The 1989 version of DYNA3D contains thirty material models and ten equations of state to cover a wide range of material behavior.