The presence of formaldehyde in the environment is due to natural processes and to man-made sources. It is produced in large quantities and has varied applications. One of the most common uses is in urea-formaldehyde and melamine-formaldehyde resins. There are several indoor environmental sources that can result in human exposure including furniture containing formaldehyde-based resins, building materials, paints, disinfectants, carpets etc. Emphasis is placed on indoor formaldehyde levels and on the ways of their reduction or elimination.