Allergen released from individual spores of the fungus Alternaria has not been investigated. Germination of spores has been suggested to increase allergen release. This study examined allergen released from individual spores and the effect of germination on allergen availability. Allergen release was determined with the Halogen (Inhalix, Sydney, Australia) immunoassay, by use of serum IgE from Alternaria -sensitized subjects and 3 Alt a 1-specific antibodies. Not all spores released allergen. Germination of the spores significantly increased the proportion that released allergen (P < .0001 for all antibodies). Alt a 1 may be a minor contributor to the total allergen released from spores except when spores have germinated. How these results reflect the allergen content of spores in the air that we breathe requires investigation.