There is growing concern about die adverse health effects of exposure to fungal bio-aerosols. The saprophytic fungus Stachybotrys chartarum (atra, SA) and its toxigenic macrocylclic tricothecene metabolites have been putatively implicated in the causation of numerous signs and symptoms of disease including fatigue, skin irritation, headache, dry cough, irritated eyes, generalized allergic symptoms and inflammation. A difficulty in evaluating individuals with possible exposure to SA and its associated mycotoxins is documentation of exposure. Currently there is no reliable biological monitoring endpoint for mycotoxin exposure. Consequently, mycotoxin exposure has been inferred from the measurement of mycotoxins in bulk samples obtained from materials such as contaminated walls, ceiling tiles, and air ducts. The toxigenic mycotoxins from SA have been shown in vitro to be potent inhibitors of protein synthesis, alter alveolar surfactant phospholipid concentrations, cause hemolysis, and modulate inflammatory reactions. The inf1ammatory and protein binding properties of SA mycotoxins suggested the potential for de novo immunogenicity. In the present work we investigated the potential immunogenicity of SA associated mycotoxins using sera from eight individuals who were exposed to numerous fungi, including SA, in a water damaged hotel. Two of these individuals had qualitatively "high" exposures, while four had "moderate" and two had "low" exposure to the SA-containing bio-aerosol. Analysis of bulk samples indicated detectable amounts of the macrocyclic tricothecenes, satratoxin and roridin, atranones, spirocyclic compounds (phenylspirodrimanes) and epidechlorogriseofulvin. In order to investigate the immunogenicity of SA exposure, we developed an enzyme-linked immunosorbent assays (ELISA) for roridin-hemisuccinate-human serum albumin (RH- HSA) specific IgG and IgM antibodies. Stored sera obtained from unrelated NIOSH studies, with no known contact to the hotel or moldy environments, were used as assay controls. Optical density measurements greater than the mean values of these controls + 3SD were considered positive. None of the tested sera gave positive RH-HSA specific-IgM antibody responses. Two of the eight individuals qualitatively exposed to "low" and "moderate" levels of bio-aerosol exposure showed positive RH-HSA specific IgG reactions. The results of this pilot serologic survey, with sera from workers in a building heavily contaminated with mycotoxin-producing fungi, indicated that individuals may make specific IgG antibodies to roridin. In a larger group of individuals exposed to SA, mycotoxin specific antibody production may be a useful adjunct to environmental monitoring in evaluating SA mycotoxin exposure and its inherent potential hazard.