For over three decades, the benefits of focus have been touted under the guiding principle that dedicated attention to a small set of linked tasks improves operating performance. Numerous studies have suggested that the performance of a division, plant, or business unit is improved to the extent that it remains focused on a narrow range of activities. Others have found similar benefits associated with focus at the level of the entire firm. A question that has received less attention, however, is whether focus at the divisional level is complementary with, or a substitute for, focus at the firm level. We explore this question by considering the performance of investigative sites in biopharmaceutical clinical trials. First, we establish that firms focusing on a particular task—at either a divisional or firm level—experience higher output and productivity with respect to that task than unfocused firms. After controlling for selection, scale, and learning effects, we find that sites that focus on conducting clinical trials significantly outperform those that mix trial activity with the provision of traditional patient care. Second, we find evidence that focus at the divisional level and firm level are substitutes. That is, organizations characterized by divisional focus alone achieve statistically similar performance to sites that are characterized by both divisional and firm focus. Copyright © 2007 John Wiley & Sons, Ltd.