Trade in services and foreign affiliate sales of services have grown tremendously over the last decade. The chapters within this thesis look at the differences needed in modeling trade and investment in professional and business services Chapter 3), the impacts of country level regulatory and investment barriers Chapter 2), methods of utilizing CGE modeling to simulate welfare gains from changes to the various types of regulatory costs operating costs, entry costs, fixed costs for establishment abroad) while incorporating the observed complex investment and trade Chapter 4) and finally also looking at the relationship between trade, foreign affiliate sales and the barriers to supplying services abroad Chapter 5). Barriers to trade in services are higher than for trade in goods. These include restrictions on foreign investment, restrictions on temporary movement of natural persons and regulatory measures that affect the entry and operations of foreign firms. Regulation can be discriminatory or non-discriminatory, but even in the latter case foreign services providers may face higher costs than local firms in complying with regulation. The papers in this dissertation contribute new modeling techniques as well as new methods of looking at the available data.