Asthmatic reactions were studied among some 130 factory workers who handled amines and other chemicals. Among present employees, 15 cases of asthma associated with occupational exposure to chemicals were found; among former employees there were at least 18. The inducing agent was judged to be piperazine in 29 persons and ethylenediamine (EDA) in 3. The asthma was of the late or dual type; immediate reactions alone were not seen. No one had attacks of asthma before employment, and atopic subjects were not preferentially affected. Routine spirometry revealed airway obstruction in fewer than half of the recent cases. Tests of nonspecific bronchial reactivity with methacholine in 6 subjects with recent asthma showed hyperreactivity in 5, while 2 subjects with earlier asthma did not have hyperreactivity. Bronchial provocation tests with piperazine in 1 subject were positive both in the factory and in the laboratory. The level of piperazine was 1.2 mg/m3 time-weighted average in a work place associated with induction of the asthmatic state and 0.3 mg/m3 in a place connected with attacks in sensitized subjects.