The precautionary principle (PP) has gained influence in environmental politics as a 'policy principle' -an idea that can spur policy change. Yet, exact definitions of the PP remain elusive, making evaluation of its actual political influence difficult. Given the controversy over the PP's meaning and policy utility, broader empirical analysis of its public formulations is overdue. Elite discourse on the PP is analysed in the search for a dominant formulation among 238 articles in a variety of disciplines. The modal PP formulation is found to be a mix of stronger and weaker elements, broadly resembling Principle 15 of the 1992 Rio Declaration. The data suggest that the principle has become weaker over time, and that its critics formulate it more strongly than proponents. Contrary to some assertions, however, American and European authors do not differ significantly in their interpretations of the PP.