Consistent with popular belief among certain academics, practitioners, and policy makers, we hypothesize that collaboration between private and public organizations promotes success. We test this hypothesis for data on clinical trial success. Contrary to this popular belief, our results do not support the beneficial effect of within- and cross-sector collaborations. In contrast, we find that trials from single private companies are four times more likely to be successful than are trials in which public and private organizations collaborate. Hence, our results indicate that companies engage with public partners to mitigate development risks, not to exchange knowledge or technologies with them.