Two types of foam insulation are in wide use. Urea formaldehyde foam is a relatively inexpensive, easily installed, and efficient insulation. Toxicity from this insulation is related to release of free formaldehyde into the home. Mild to incapacitating symptoms have been reported in occupants of urea formaldehyde-insulated homes. Airborne formaldehyde levels frequently have exceeded standards set for occupational exposure. The long-term consequences of such exposure are unknown. Because of publicity over the toxicity of urea formaldehyde foam, many physicians and patients have confused urea formaldehyde and polyurethane foam. Unlike urea formaldehyde, polyurethane foam is fully cured before construction. Toxicity occurs only during manufacture and curing. To date, there have been no reports to our knowledge of toxicity in occupants of polyurethane-insulated homes. However, toxicity caused by pyrolysis products may occur during combustion in homes insulated with either type of insulation. This report details 48 patients in whom complete medical data were obtained out of the first 100 patients contacting the Rocky Mountain Poison Center.