In addition to the important role of memory strategies in mediating age changes in recall performance, it is clear that the permanent memory system (or information available in the knowledge base) exerts a significant influence on the acquisition and retention of information. Age changes in memory performance will be fully understood only through the investigation of the interrelationships among memory processes and the evolving knowledge base. It seems likely that the knowledge base can affect memory performance either "directly" or mediated via the operation of deliberate memory strategies. Research on verbal rehearsal and organization provides an example of the "direct" case. Given a stimulus list with a strong built-in organization (such as a set of taxonomic categories presented in a blocked fashion), children who are active and passive rehearsers show minimal differences in performance. Investigations of the mediated case concern the effects of stimulus familiarity on rehearsal and recall. Preliminary data suggest that extended familiarity with to-be-remembered materials, perhaps resulting in stronger inter-item associations in the knowledge base, may be critical for the maximally efficient execution of active rehearsal techniques. This and other findings suggest that the implementation of a deliberate organizational strategy is not content free, but rather depends upon the nature of the to-be-remembered material to which the strategy is to be applied. (Author/SS)