Three experiments investigated the acquisition of English epistemic modal verbs (e.g., "may", "have to"). Semantically, these verbs encode possibility or necessity with respect to available evidence. Pragmatically, the use of weak epistemic modals often gives rise to scalar conversational inferences (e.g., "The toy may be under the sofa" implies that it is not certain that the toy is under the sofa). Experiment 1 showed that children between the ages of 4 and 5 have mastered key aspects of epistemic modal semantics but have difficulties with contexts involving epistemic possibility. Experiment 2 showed that 4-5-year-olds prefer stronger/more informative over weaker modal statements in contrastive contexts if the stronger statements are warranted by the evidence. Experiment 3 further demonstrated that children of this age can draw pragmatic inferences from the use of weak epistemic modal verbs in contexts that do not involve overt pragmatic judgments. Taken together, these findings throw light on the acquisition of epistemic modality and have implications for the development of the semantics-pragmatics interface.