Topological Defects: Fossils from the Early Universe

In the context of current particle physics theories, it is quite likely that topological defects may be present in our universe. An observation of these fossils from the early universe would lead to invaluable insight into cosmology and particle physics, while their absence provides important constraints on particle-cosmology model building. I describe recent efforts to address cosmological issues in condensed matter systems such as He-3 and a possible solution to the magnetic monopole problem due to defect interactions. (Invited talk at the 1997 RESCEU Symposium, University of Tokyo.)