This paper empirically examines how business unit reorganization affects innovation, and explores how the learning process may mediate this relationship. Unit reorganization is the creation, deletion, or recombination of business units within a firm. Innovation is radical and involves product market entry by a firm into markets in which it was not previously active. I test competing hypotheses that predict either a U-shape or inverted U-shape relationship between reorganization and innovation to determine whether and how learning occurs in the presence of unit-level structural change. Theoretical support is drawn from literature on dynamic capabilities and organizational learning. The sample studied is 250 medical firms belonging to the pharmaceutical, healthcare-service, and medical-device industries, studied over a 20-year period. The findings are twofold. First, reorganization is found to exhibit a U-shape relationship with innovation, supporting learning arguments that stress the importance of experiencing a cohort of multiple events. Second, only reorganization experiences within a current period affect future innovation; past experiences do not impact future innovation, implying that firms may face constraints in organizational memory. The study concludes by exploring the structural origin (i.e., from internal, acquired, or recombined units) of innovative activity within firms.