Rats show a pronounced preference for the tastes of starch-derived polysaccharides. Three of these compounds--Polycose, maltotriose and amylopectin--were used along with a standard array of chemicals in a study of their effectiveness as taste stimuli, as monitored by evoked single unit activity in the nucleus tractus solitarii (NTS). Maltotriose and amylopectin elicited very few spikes and no clear quality-related pattern of neural activity. Polycose, however, was an effective taste stimulus. It evoked an activity profile across neurons and over time that was poorly correlated with that of the prototypical sugar (sucrose) and only moderately related to those of the non-sugar prototypes (NaCl, HCl and quinine-HCl). The 14 cells (23%) that responded particularly well to Polycose were all members of neuronal subgroups that emphasized salt, acid and quinine sensitivity. Thus, despite the strong behavioral preference shown to Polycose, its neural profile is unlike those of other preferred stimuli. Polycose may represent a unique taste stimulus whose quality cannot be readily associated with those of the traditional 4 basic tastes.