This paper explores how firmspsila alliance portfolios are related to patent output in the biotechnology industry. We propose that patent output is related to the composition of the firm's alliance portfolio, including the diversity of technologies, depth and scope of technologies, extent of alliance partner cospecialization, entry stage of technology development, and extent of prior alliance partner experience. We draw from real-options-based and knowledge-based views to develop a typology of alliance portfolios, arguing that each portfolio type differs in its effects on intra- and interorganizational dynamics, and thus, on patent output. Our proposed typology suggests that biotechnology firms follow four types of alliance portfolio strategies: focus, hedge, enable, and combine. Using secondary data provided by the ReCap, Delphion, and Compustat databases on 827 biotechnology alliances among 353 firms from 1995 to 2003, we found support for our proposed typology. Empirical results showed that firms with focus and hedge alliance portfolios had greater patent output than firms with enable or combine portfolios, and firms with focus alliance portfolios had the greatest patent output. We conclude with a discussion of our key findings along with implications for theory, future research, and management practice.