Prompted by referral of a printer with aplastic anemia, a study of possible marrow toxicity of workplace substances was undertaken. Dermal and respiratory exposures to dipropylene glycol monomethyl ether, ethylene glycol monoethyl ether, and a range of aliphatic, aromatic and halogenated hydrocarbons used for offset and ultraviolet cured multicolor printing were documented. Evaluation of seven co-workers revealed normal peripheral blood pictures, but bone marrow specimens demonstrated clear patterns of injury in three while the others had nonspecific signs of marrow effect. These changes could not be explained by known risk factors. The authors conclude that further evaluation of possible bone marrow toxicity resulting from exposure to glycol ethers and ultraviolet curing printing processes is warranted. More generally, we have provided data demonstrating that peripheral blood counts may be an insensitive tool for the study of hematologic toxins acting at the bone marrow level.