Older adults, even those with normal or near-normal audiograms, report greater subjective listening difficulty in everyday life compared to younger adults. However, their difficulties are not well predicted from pure-tone or speech audiometry in quiet or noise. Speech intelligibility tests based on word recognition do not incorporate many of the sensory and cognitive challenges that listeners confront in everyday situations where it is necessary to understand a target talker when there are competing talkers in the auditory scene. Speech-in-speech intelligibility is affected by age-related differences in auditory and cognitive processing. Age-related differences in auditory temporal processing reduce access to periodicity and temporal envelope cues that serve stream segregation and spatial listening. Age-related differences in cognitive processing are reflected in difficulty remembering speech heard in multi-talker babble or switching spatial attention when there is uncertainty about the location of a target talker in a multi-talker display. Furthermore, when listening occurs in multi-tasking conditions (e.g., listening while walking), there are increased and competing demands for cognitive resources that may affect performance on listening and/or the competing tasks. These examples highlight the importance of both inter- and intra-individual differences in speech-in-speech intelligibility that depend on the interaction of auditory and cognitive processing abilities.