Most measures of naturalistic human memory instruct participants to recall personally-experienced episodes in narrative format. These narratives contain non-episodic details, such as general knowledge of the world, or personal knowledge about one’s life circumstances that are elevated with aging. As this non-episodic content is incidental to the instructions, it is difficult to interpret. We modified the widely used Autobiographical Interview (AI) to create a Semantic Autobiographical Interview (SAI) that explicitly targets personal semantic (P-SAI) and general semantic memories (G-SAI). We tested the SAI in young and older adults, alongside with the original AI. Older adults produced a higher proportion of off-task utterances (i.e., details not probed by instructions) across all sections of the interview. Specifically, older adults produced more autobiographical facts in the AI, more episodic and general semantic details in the P-SAI, and more self-knowledge in the G-SAI than did young adults. However, older adults also consistently produced more probed autobiographical facts than did young adults on the P-SAI. These findings suggest that the increased production of semantic details in ageing reflects a bias towards age differences in autobiographical recall that goes beyond episodic remembering, as reflected by an age-associated abundance of semantic details across sections of the interview, findings that are not accommodated by accounts of aging and memory emphasizing reduced cognitive control or compensation for episodic memory impairment.