Metal workers exposed to trichloroethylene for the degreasing of metals were studied to evaluate the genotoxicity of this exposure. For 15 workers presently exposed to high doses of trichloroethylene there was no difference from unexposed persons with respect to sperm count and morphology, and a small increase of two fluorescent bodies (YFF%) in spermatozoa. In contrast, there was a highly significant increase in frequency of structural aberrations (breaks, gaps, translocation, deletions, inversions) and hyperdiploid cells in cultured lymphocytes from trichloroethylene degreasers. As control groups, physicians from chemically non-exposed surroundings and a concurrently sampled reference from cytogenetic investigations were used. This study indicates positive correlations between exposure to trichloroethylene and somatic chromosome aberrations, whereas no effect on male germ cells could be demonstrated.