Abstract Recent research on reasoning has resulted in a number of authors urging a convergence between ideas in the hitherto disparate fields of deduction and decision making. The deontic reasoning literature in particular refers increasingly to the decision-making constructs of subjective utility and subjective probability. Although the former construct has received some attention from experimenters, the latter has remained relatively unexplored. In this paper a set of experiments is reported in which a modified form of Wason's selection task using an enlarged array was used to investigate the role of a probabilistic factor in reasoning with conditional obligations. Results showed that this factor played a significant role in mediating this reasoning, when probabilistic information was added both to antecedent and to consequent items. Other results indicated that the effect occurred principally by suppressing selections of items with relatively low subjective relevance.