Formaldehyde (FA), which is an important chemical with a wide commercial use, has been classified as carcinogenic to humans by International Research on Cancer (IARC). The genotoxic and carcinogenic potential of FA has been documented in mammalian cells and in rodents. A recent evaluation by the E.U. Scientific Committee for Occupational Exposure Limits (SCOEL) anticipated that an 8-h time-weighted average exposure to 0.2 ppm FA would not be irritating and not genotoxic in humans. In order to verify this prediction, a field study was performed that aimed at evaluating immune alterations and genetic damage in peripheral lymphocytes of workers in medium density fiberboard plants exposed to a level of FA equivalent to the OEL recommended by SCOEL (0.2 ppm). Subsets of peripheral lymphocytes, immunoglobulins (IgG, IgA, IgM), complement proteins, and tumor necrosis factor-alpha (TNF-alpha) levels were evaluated. DNA damage of the workers was assessed by the Comet assay. The absolute numbers and the percentages of T lymphocytes and of natural killer cells, and the levels of TNF-alpha were higher than the controls, whereas IgG and IgM levels were found to be lower in workers. Other examined immunological parameters were not different from those of the controls. There was no increased DNA damage in the workers compared to controls.