Finished basements in twenty-seven Ottawa houses were investigated to determine if the basement assemblies could contribute to poor indoor air quality due to molds. The wall cavities were inspected with optical fibrescopes to determine the composition and note the conditions. Visible mold colonies were sampled to identify mold species. The presence of molds correlated with the presence of chronic wetting events rather than any particular basement finishing techniques. Molds were analyzed from 16 (59%) of the houses and toxigenic molds were found in all houses except one.