The controversies surrounding BSE and the seal deaths show two aspects of Osterhaus' role. He was self-confident in his estimations about risks, but also acknowledged criticism from his sceptics. The tricky question was when to stick to his original position, and when to adopt the opposing view, and, consequently, the appropriate strategy. This, he says, created a tension: on the one hand he had his own gut feelings, and at the same time he tried to think through competing viewpoints. There was not only an epistemological choice to be made, but also a balancing act to carry out: considering various interests and health threats. We will characterise his role as that of the strategic scientist: someone who carefully balances different viewpoints and forms of evidence, but who also has the strategic skills and will to further his own case.