Eleven male workers from the polymerization department of a vinyl chloride factory, seven people employed in the laboratory of another vinyl chloride plant, and ten controls from outside the factory environment were examined for the presence of chromosome aberrations in blood lymphocytes. Chromosome anomalies such as fragments, rings, translocations, and dicentrics were observed in most of the workers from the polymerization department. However, the medical history of these workers shows that they received frequent radiographs of the hands, feet, vertebral column, and digestive tract. It is therefore impossible to determine whether these chromosome anomalies result from vinyl chloride exposure.