In this dissertation, structural models that utilize parametric and nonparametric approaches are developed that are used to measure competition and cost efficiency in the US banking industry (1990--96). Competition in loan and deposit markets is studied using the method of conjectural variations (Bresnahan, 1982). The results indicate that market imperfections present are negligible, and that loan and deposit services are competitively priced. Cost efficiency is studied using a stochastic cost frontier in the spirit of Bauer (1990), and cost increases above optimal levels are assigned to technical and allocative inefficiencies. The results indicate that technical inefficiency is the major cause for deviations from the cost frontier and allocative inefficiency is declining during this period.