Few studies have compared interference-based forgetting between item versus associative memory. The memory-system dependent forgetting hypothesis (Hardt, Nader, & Nadel, 2013) predicts that effects of interference on associative memory should be minimal because its hippocampal representation allows pattern separation even of highly similar information. In contrast, there should be strong interference effects on extra-hippocampally represented item memory. We tested this prediction in behavioral data from 3 experiments using continuous recognition paradigms. Given older adults' greater deficits in associative than item memory, we also compared younger and older adults to test whether this associative deficit extends to greater interference susceptibility in older adults' associative memory. Experiment 1 examined item-item associative memory with participants studying unrelated word pairs continuously intermixed with item (single words) and associative (intact vs. recombined pairs) recognition tests across interference-filled lags. Experiments 2 and 3 examined item-context (i.e., source) associative memory with participants studying words in different spatial positions continuously intermixed with source-monitoring tests (presented on top vs. on bottom vs. new?) across interference-filled lags (Experiment 3 controlling for delay/decay-based effects). In all experiments, item memory declined from the first lag on. In contrast, associative memory initially remained stable, with strong evidence for null effects of interference even in older adults, but showed some declines at later lags. The data supports Hardt et al.'s proposal of differential interference-based forgetting in item versus associative memory. The results further show that the age-related associative memory deficit does not extend to greater interference-based forgetting in older adults' associative memory.