Rats conditioned to avoid drinking a sucrose solution or a glucose solution were tested for generalization of the learned aversion to three lower concentrations of these sweeteners. The behavioural responses indicated two types of discrimination. The first one, after two seconds, is of a qualitative nature; the second one, after five seconds, is of a quantitative nature showing an aversive response depending on the concentration. Cross-aversion to ten gustatory stimuli showed on the basis of the qualitative discrimination that the rats discriminate between the different sweeteners in a similar way as man does.