The effect of a gymnemic acid (GA) rinse, which simulated a sweet-taste deficit, was measured on human taste perception and identification. Taste ratings showed that GA reduced the intensities of sucrose and aspartame to 14% of pre-rinse levels; over the recovery interval of 30 min, these values increased linearly to 63% of the pre-rinse levels. Repeated presentations of a set of 10 stimuli (five primarily or partly sweet--sucrose, aspartame, and NaCl-sucrose, acid-sucrose and quinine-sucrose mixtures; and five nonsweet--NaCl, KCl, Na glutamate (MSG), quinine HCl and citric acid) for identification following water and GA rinses produced 'taste confusion matrices' (TCMs). Correct identification of the sweet-tasting stimuli was reduced by 23% in presentations closely following the GA rinse, an effect that dissipated with time. Most misidentifications involved sucrose and mixtures containing sucrose. In a second TCM experiment, GA was presented frequently within each session to maintain the sweet taste deficit, which revealed itself as specific confusions. Rinsing with GA impaired discriminability of sweet-nonsweet pairs of stimuli but enhanced discriminability of the aspartame-(NaCl-sucrose) pair. GA had no effect on discriminability of nonsweet stimulus pairs. The results suggest that specific error patterns in the TCM could be used to identify quality-specific taste disorders.