Paper discusses Plains-Southwest interactions and relationships. Utilizing both archeological and ethnographic evidence, author provides useful information ranging from the Paleo-Indian to the Historic Period for Plains-Southwest contact. Positing migration, either group or individually, trade, diffusion by simple contact, warfare and competition and population pressure as causal factors, author delineates available evidence and general trends and changes through time. He concludes that "the boundary between the Southwest and the Plains would seem to have been both cultural and geographic" which resulted in a dichotomy between the Plains and the Southwest.