On exposure to pancreatic extract (PE), four parents of cystic fibrosis (CF) children developed immediate hypersensitivity-like symptoms: i.e. rhinoconjunctivitis, asthma, and/or anaphylaxis. IgE to PE was demonstrated in the subjects by skin testing, leucocyte histamine release and radioallergosorbent test (RAST). No serum precipitating antibodies were found. Bronchial challenge caused an immediate asthmatic response. No delayed asthmatic response or hypersensitivity pneumonitis-like reaction occurred. The responsible antigen for PE induced asthma is unknown; trypsin failed to inhibit PE-RAST and is therefore not responsible in these subjects. Caution should be exercised in using PE for skin testing and bronchial challenge in subjects with suspected hypersensitivity to PE. Certain measures were found useful in preventing the occurrence of symptoms in the four subjects.