Formaldehyde is a low molecular weight chemical and can elicit acute and chronic health related problems. Most of the inhaled formaldehyde is retained in the upper respiratory tract due to its extraordinary solubility. Therefore, cases of formaldehyde-induced occupational asthma are sporadic despite its widespread use in industrial processes. We herein report upon a case of occupational asthma due to formaldehyde, which was confirmed by workplace challenge including working environmental assessments, and by formaldehyde inhalation challenge using a specially designed closed-circuit apparatus. To investigate the possible involvement of an IgE-mediated mechanism, both in vitro and in vivo tests were done. IgE antibody specific for formaldehyde-human serum albumin conjugate (F-HSA) was not detected by ELISA, and no specific cutaneous reactivity to F-HSA was noted by either skin prick or intradermal test. The patient was diagnosed with formaldehyde-induced occupational asthma not associated with an IgE mediated mechanism.