We report two asthmatics working in the same factory who exhibited late asthmatic responses (LAR) to ethylenediamine (EDA) vapor. After several months of exposure to EDA, both patients developed productive coughing, wheezing, and dyspnea. Provocative inhalation tests using EDA evoked LAR in both patients, but it did not evoke any asthmatic symptoms in healthy subjects. IgE antibodies to EDA examined by intracutaneous and P-K tests were detected. It appears that, in these two cases, LAR are mainly due to immediate-type allergic reactions.