In 4 experiments the authors used 2-stage designs to study susceptibility to interference in human discrimination learning. The experiments used a food allergy task. In Experiment 1, participants were presented with a discrimination in Stage 1 in which Food A predicted an allergy outcome (A → O). In Stage 2, when combined with Food B, Food A predicted the absence of the allergy (B → O, AB → no O). In the test phase, Food A was found to have retained its Stage 1 association with the allergy despite the potentially interfering Stage 2 trials. In Experiment 2, a discrimination between 2 compounds (AB → O, CD → no O) remained intact despite subsequent complete revaluation of the elements, (A → no O, B → no O, C → O, D → O); in Experiments 3 and 4, a discrimination between 2 pairs of elements (A → O, B → O, C → no O, D → no O) remained intact despite subsequent complete revaluation of the AB and CD compounds, (AB → no O, CD → O). These experiments yielded evidence of remarkable resistance to interference in human discrimination learning. The results are at variance with the predictions of J. M. Pearce's (1987, 1994a) configural theory of associative learning.