Flooding in New Orleans (NO) after Hurricanes Katrina and Rita caused extensive mold growth in homes resulting in public health concerns. We conducted an environmental assessment of homes to determine the type and extent of mold exposure. We used a geographic information system to randomly select 112 homes, stratified by water damage and then visually assessed mold growth. Homes were classified with heavy mold coverage if mold covered >50% of the walls in the most mold-damaged room and by flood level as high (>6ft), medium (3-6ft), or low (<3ft). Air samples from a subset of 20 homes were analyzed for culturable fungi, fungal spores and markers of mold (a(1, 3-1, 6)-glucans) and bacteria (endotoxin); geometric means and standard deviations (GSD) were calculated. Mold growth occurred in 51 (45.5%) homes; 19 (16.9%) had heavy coverage. Flood levels were high at 21 (18.8%), medium at 19 (17.0%), and low at 72 (64.3%) homes. Seventy-six (67.9%) had roof damage with water leakage. Predominant fungi indoors were Aspergillus, Penicillium, and Trichoderma. Geometric mean air levels for a(1, 3-1, 6)-glucans were 1.6 ug/m3 (GSD 4.4) indoors and 0.9 ug/m3 (GSD 2.0) outdoors; endotoxin levels were 23.3 EU/m3 (GSD 5.6) indoors and 10.5 EU/m3 (GSD 2.5) outdoors.We estimate that over 110,000 residences have elevated mold and bacteria levels and over 40,000 have heavy mold growth in the NO area. Levels of microbial exposure markers exceeded those previously associated with health effects. Residents should follow CDC recommendations developed following the 2005 hurricanes for appropriate precautions when entering or cleaning affected homes.