This study examines effects of memory load on the processing of scalar implicature via a dual-task paradigm using reading span and self-paced reading. Results indicate that participants showed online sensitivity to underinformative sentences (e.g., "Some birds have wings and beaks") at the end of the sentence. This online sensitivity disappeared when participants were under increased memory load. Moreover, participants in the memory-load condition did not show sensitivity to semantically false sentences (e.g., "All books have pictures and drawings"). These results pose important conceptual and methodological questions of: (1) whether the processing cost associated with scalar implicatures can be attributed to general proposition evaluation rather than scalar implicature derivation per se (Bale et al. in Semant Linguist Theory 20:525-543, 2010); and (2) to what degree memory load affects implicature computation only. I conclude with a discussion of these two issues for future research.