The following is a review of some of the work that we have done since 2007 regarding the importance of molds in the phenomenon of sick building syndrome (SBS). In these studies we first examined mold contamination in air handling units (AHU). Our results showed that Cladosporium sp. were commonly recovered in AHU as growth sites and free spores. They were found mainly on the blower wheel fan blades, the ductwork, and cooling coil fans. Our results showed that the presence of species of molds other than Cladosporium in locations other than the blower wheel blades indicated that the AHU condition was not optimal. The finding of Cladosporium species on blower fan blades does not necessarily indicate that the AHU is in poor operating condtion. In a series of three papers, we examined growth and mycotoxin production by Chaetomium globosum (CG). In these studies we showed that CG produces two potent mycotoxins, chaetoglobosin A (Ch-A) and chaetoglobosin C (Ch-C) when grown on building material. We discovered that these toxins break down when exposed to temperatures in excess of 75ºC. We also showed that growth and mycotoxin production by CG is favored at a neutral pH. In another study, we showed that mycotoxins can be detected in body fluids and human tissues from patients exposed to mycotoxin producing molds, and we showed which human tissues or fluids were the most likely to give positive results for detection of these compounds. Finally, we showed that the macrocyclic trichothecene mycotoxins (MTM) produced by Stachybotrys chartarum (SC) are detectable in experimental animals soon after exposure and we described the dynamics of MTM tissue loading.