Approximately 40% of American buildings are moldy. Early studies found that neurologists could not differentiate between people who lived or worked in moldy buildings and patients with mild to moderate traumatic brain injury—they had the same neurological and cognitive deficits. Our laboratory developed a mouse model to determine how mold exposure might lead to cognitive dysfunction. One critical issue is whether exposure to any mold causes problems or only exposure to extremely toxic molds like Stachybotrys. We therefore quantified the effects of exposure to (1) intact Stachybotrys spores (IN) containing a variety of toxins, volatile organic compounds and proteinases, (2) Stachybotrys spores extracted twice with ethanol (EX) to remove toxins and denature proteins, or (3) the nonpyrogenic saline vehicle (VEH). Mice were nasally instilled 3X per week. After 5 weeks, EX mice performed significantly worse in finding the hidden platform in the Morris water maze (MWM) than VEH or IN mice, taking longer to find the platform and using longer paths. Surprisingly. IN mice showed evidence of lesser memory impairment. MWM performance in EX and IN mice was inversely correlated with numbers of interleukin-1β cells in dorsomedial CA1 as well as with weight gain over the first 3 weeks of treatment. Clearly, exposure to just the mold skeleton is sufficient to cause brain inflammation and cognitive deficits, suggesting exposure to any mold could be problematic.