Empirical studies of mergers and acquisitions typically focus on firm-level financial performance. In contrast, we use human capital theory to model these events as transactions that simultaneously have cross-level, real effects on workers, plants, and firms. Our empirical analysis is based on longitudinal, linked employer-employee data for virtually all Swedish manufacturing firms and employees. We find that mergers and acquisitions enhance plant productivity, although they also result in the downsizing of establishments and firms. Firm performance does not decline in the aftermath of these ownership changes. We conclude that such transactions constitute a mechanism for improving the sorting and matching of plants and workers to more efficient uses. Copyright © 2010 John Wiley & Sons, Ltd.