Financial theory posits that capital markets convey through stock prices their expectation of the firm's future performance. We use concepts from Principal-Agent Theory and Prospect Theory to provide a theoretical explanation for the role stock price variation plays in managerial decision-making. We then empirically investigate what specific decisions managers undertake in response to stock price variation.We perform our empirical analyses in the context of the pharmaceutical industry. We find that drug firms whose stock under-performed the industry react differently than drug firms with high performing stocks.Specifically, laggards tend to implement more changes to their current product portfolio and distribution than high performing firms. And, the more laggards under-perform, the more they implement acquisitions aimed to produce immediate improvement in the firm's product portfolio. In contrast, drug firms whose stocks out-perform the industry tend to make fewer changes to their current portfolio and distribution.Instead, they focus more on long-term R&D and marketing of existing products. We interpret these findings in light of industry key success factors.Wyeth "has many issues to resolve before it can realize… bright future, Essner [Wyeth's Executive VP] admits. He lists the following: remaining an independent company, settling the diet-drug litigation, attracting good people, and maintaining stock performance at the top." (Pharmaceutical Executive 2000, p.68).