Interaction has been argued to promote noticing of L2 form in a context crucial to learning--when there is a mismatch between the input and the learner's interlanguage (IL) grammar (Gass & Varonis, 1994; Long, 1996; Pica, 1994). This paper investigates the extent to which learners may notice native speakers' reformulations of their IL grammar in the context of dyadic interaction. Thirty-three adult ESL learners worked on oral communication tasks in NS-NNS pairs. During each of the five sessions of dyadic task-based interaction, learners received recasts of their nontargetlike question forms. Accurate immediate recall of recasts was taken as evidence of noticing of recasts by learners. Results indicate that learners noticed over 60-70% of recasts. However, accurate recall was constrained by the level of the learner and by the length and number of changes in the recast. The effect of these variables on noticing is discussed in terms of processing biases. It is suggested that attentional resources and processing biases of the learner may modulate the extent to which learners "notice the gap" between their nontargetlike utterances and recasts.