Interorganizational relationships are recognized as an increasingly important source of competitive advantage. Hence, goal-oriented management of the alliance portfolio--all the alliances of the focal firm--plays a decisive role in company performance. Consequently, the configuration and development of the alliance portfolio become important strategic issues. In light of that, this article develops theoretical propositions that seek to clarify what determines the configuration and evolution of an alliance portfolio, and then presents the results of a longitudinal study to illustrate the developed theoretical framework. Building on contingency theory and a coevolutionary framework, we were able to identify three distinctive types of portfolio strategies at business level and to illustrate how they interact with the development of the business strategy and the business environment. Encompassing all this, the study illustrates and explains developmental paths and patterns in the evolution of an alliance portfolio. The developmental course typically evolves from adapting to shaping and to exploiting (stabilizing), according to the state of strategic uncertainty and the firm's resource endowment. A sudden increase in exogenous strategic uncertainty, however, can lead to a strategic shift back to an exploration or hybrid strategy.