Four experiments investigated the impact of the lexical status of memory and processing stimuli on complex memory performance, with the aim of exploring mechanisms of interference in working memory. In a complex memory task, participants recalled words or nonwords while either monitoring words or nonwords for phonological content, or suppressing articulation. In groups of 9- and 10-year-old children and adults, word recall was significantly more impaired by monitoring words than nonwords. A converse disturbance of nonword recall by nonword monitoring was consistently found for adults, but was less marked in the child groups. It is proposed that interference in complex memory tasks reflects the operation of two distinct processes: a lexical-semantic process of either interference between memory and processing stimuli or redintegration, and the strategic use of lexical status to discriminate potential target from non-target items. Whereas the former process is invariant with age, the latter strategy is robust in adults but in the early stages of emergence with the younger participants.