Real options reasoning (ROR) is a conceptual approach to strategic investment that takes into account the value of preserving the right to make future choices under uncertain conditions. In this study, we explore firms' motivations to invest in a new option. We find, based on an analysis of a large sample of patents by firms active in the pharmaceutical industry, that their investments in R&D are consistent with the logic of ROR. We identify three constructs—scope of opportunity, prior experience, and competitive effects—which have an influence on firms' propensity to invest in new R&D options and which could usefully be incorporated in a strategic theory of investment. Copyright © 2003 John Wiley & Sons, Ltd.