This chapter covers the economic theory and evidence about the impact of provider consolidations (mergers and acquisitions) in healthcare services. As expected, hospital combinations within local markets (horizontal) are associated with higher unit prices but no measurable improvement in metrics of quality or outcomes. Prices increase by about 15%. Currently 30%–40% of the US population lives in big cities with competitive hospital markets. However, an equal fraction lives in smaller cities that could support more competitive hospitals; public policy to encourage competition there would be appropriate. The chapter investigates economic theories of vertical integration across markets; results here are less robust. An example of enhanced market power through bundling is provided, but a health system’s ability to do so is limited by lower administrative cost to employers of dealing with a single insurer that covers sellers in such markets.