Various task constraints were imposed on subjects making same/different, AX discriminations within and between phonetic categories. The experiments employed four 50‐ms, synthetic vowels from an/i/‐/I/continuum and five interstimulus delays (0‐2000 ms). In the first experiment, stimuli were presented with all trial types randomized together or with between‐ and within‐category shifts in separate trialblocks. Between‐category performance was superior with separate blocks, whereas within‐category performance did not differ in the two procedures. A second experiment involved AX presentations to subjects who were or were not initially informed of the intended category labels. Surprisingly, category knowledge improvedwithin‐categorydiscriminations. In a third experiment, subjects were required to identify both vowels in an AX pair. Between‐category discrimination was higher, and within‐category discrimination lower, with AX identification as compared to a same/different response. The results of these experiments suggest that a stable phonetic and an unstable auditory short‐term memorybothcontribute to within‐andbetween‐category discrimination, with some labeling occurring on a comparative basis. Furthermore, task demands alter the relative contributions of auditory and phonetic memory.