This article investigates portfoliomanagement in double unknown situations. Double unknown refers toa situation in which the level of uncertainty is high and both technology and markets are as-yet-unknown. This situation can be an opportunityfor new discoveries, creation of new performance solutions and giving direction to portfolio structuring. The literature highlights that the double unknown situation is a prerequisite to designinggeneric technologies that are able to address many existing and emerging markets and create value across a broad range of applications. The purpose of this paper is to investigatethe initial phases of generic technology governance and associated portfolio structuring in multi-project firms.We studiedthree empirical contexts of portfolio structuring at the European Semiconductor provider STMicroelectronics. The results demonstrate that 1) portfolio management for generic technologies is highly transversal and comprises creating both modules to address market complementarities and the core element of a technological system – the platform and 2) the design of generic technologies requires "cross-application" managers who are able to supervise the interactions among innovative concepts developed in different business and research groups and who are responsible for structuring and managing technological and marketing exploration portfolios within the organizational structures of a company.