This work explores the roles of potential simultaneity and heterogeneity in determining firms' decisions to engage in R&D collaboration, using a sample of Italian manufacturing firms. Partnerships with other firms, research institutions, universities and other small centres are considered jointly by applying a multivariate probit specification. This allows for systematic correlations among different cooperation choices. The results support the hypothesis that the four cooperation decisions are interdependent. The decision to cooperate in R&D differs significantly depending on the cooperation options. Public support, the researcher intensity and the size are all of importance in determining R&D alliance strategies.