We investigated associative learning as a possible explanation of overperception in asthma. Thirty newly diagnosed patients with asthma (eight men) underwent a histamine provocation to elicit airway obstruction (Cockcroft's protocol). Patients testing positive and reporting symptoms underwent an identical procedure on the next day with saline, a substance that does not elicit any significant airway changes. Symptoms of airway obstruction and fatigue increased significantly from pre- to post-saline inhalation on day 2, whereas physiological parameters did not change. Increases in symptoms were significantly related to the level of dispositional negative affectivity, but not to the degree of airway reactivity or changes in objective lung function. These results suggest that the experience of asthmatic symptoms in a specific context may evoke the experience of similar symptoms when confronted with the context only. Learning was more likely to occur in those patients with high negative affectivity.