The stress fields of an infinite and a finite screw dislocation wall are given and from them the interactions of the screw dislocation walls with parallel and nonparallel dislocations have been studied. The nature of the penetration through a screw dislocation wall of a number of parallel screw dislocations driven by external stress and the possible stress concentration for a pileup against the wall are discussed in detail. The forces exerted by a screw dislocation wall on nonparallel edge and screw dislocations are calculated. The significance of the local torques due to these forces as a possible mechanism for the screw dislocation wall to become a source for generating dislocations is pointed out. The metastability of the screw dislocation walls is demonstrated and their strain energy is estimated and compared with that of the edge dislocation walls. It is concluded that the resistance to penetration of a dislocation wall increases in the following order: infinite edge dislocation wall, finite edge dislocation wall, finite screw dislocation wall, and infinite screw dislocation wall. It is also found that the strength of a dislocation wall increases with its surface strain energy.