It has been proposed that the formation of episodic associations between stimuli may involve different processes when memoranda are from the same or different perceptual domains, and when stimuli are experienced concurrently or sequentially. Such differences are postulated to determine the degree of unitization of memoranda, and are asserted to influence whether such associations are later retrieved via familiarity or recollection. In two experiments utilizing the context effects (CEs) paradigm, we examined effects on associative memory observed when unitization of memoranda is not readily achieved, due to domain differences between stimuli or to asynchronous presentation. In both cases, the standard associative-binding CE of better recognition of probes under contextual reinstatement (i.e., higher hit rates for pairs of repeated probes vs. re-paired probes) was only found when participants explicitly recognized the context stimuli. These results contrast with earlier findings that for concurrent encoding of same-domain stimuli, CEs are obtained even in the absence of explicit memory for contexts. The contrast supports the assertion that in the absence of unitization associative memory is dependent on recollection, while unitized associations may be supported by familiarity strength. (Contains 4 figures.)