Occupational asthma is characterised by airway inflammation, variable airflow limitation and airway hyperresponsiveness related causally to work. The aim of the study was to ascertain whether in patients with occupational asthma findings persist after withdrawal from occupational allergen exposure. A group of 37 patients with occupational asthma and a control group of 19 persons were examined. Results in asthmatics obtained during the first visit when occupational asthma was acknowledged, were compared with recent results about 6.5 yr on average after elimination of occupational allergen exposure. Recent findings in occupational asthma patients were compared with the control group. In patients with occupational asthma, no significant differences were found between results obtained at the first and recent visit. Symptoms of asthma persisted in as much as 86.5% of patients. During recent examination there were more positive results in asthmatic patients comparing with the control group in histamine challenge (61.3 vs. 5.3%, p<0.01), eosinophile cationic protein (41.7 vs. 5.3%, p<0.05), prick tests (45.9 vs. 10.5%, p<0.05). Positive results of the present histamine challenge test and elevated eosinophils in sputum were more frequent (p<0.05) in patients with occupational asthma due to high molecular weight allergens than to low molecular weight allergens.