This dissertation investigates the effects of consolidation and common ownership in hospital and pharmaceutical markets. In the first chapter, I develop a multi-product production function framework to assess whether hospital mergers yield efficiencies. Unlike prior studies that separately estimate impacts on cost and quality, I incorporate both into a unified model that captures how acquisitions may shift the quality-quantity frontier through gains in total factor productivity. I then conduct a retrospective merger analysis to measure the effects of acquisitions on productivity and costs. I find that mergers increase target hospital productivity by 5 percent on average and reduce inpatient marginal costs by 3 percent, with no significant effect on outpatient costs. A heterogeneity analysis suggests mechanisms underlying these gains and their potential to pass through to prices. The second chapter, joint with Atul Gupta, Alex Olssen, and Tong Liu, examines whether merger-driven cost savings pass through to hospital prices using transaction-level data on hospital outpatient care in California. We show that system ownership leads to both price increases and cost synergies for independent hospitals, but not for hospitals already under system ownership. Using a structural model of patient demand and hospital-insurer bargaining, we find that acquiring systems target hospitals with weak bargaining power. Although about half of cost savings are passed through to insurers, the small size of acquired hospitals relative to systems limits the overall price impact. The third chapter explores the welfare implications of common ownership of biotechnology startups. Venture capital firms often hold stakes in multiple competing startups, allowing them to reduce R&D duplication. Estimating a three-stage model of drug development and competition, I illustrate a welfare trade-off: common ownership lowers R&D costs but reduces competition in the product market. Under an assumption of homogeneous development costs, the model suggests that cost savings dominate in smaller markets, while competition losses prevail in larger ones.