In this histochemical study on the ocular lens, the authors test for the presence of various sorts of the (unsaturated) polycyclic aromatic hydrocarbon (PAH) in 66, both clear and cataractous human lenses. A statistically significant greater amount of PAH is found in the cataractous lenses studied (p < 0.01), with two kind of PAH, phenanthrene and 1,2-benzoanthracene, appearing exclusively in lenses with cataracts. The authors put forward a hypothesis on the cataractogenic effect of PAH on the basis of its interference with lens metabolism and the subsequent production and release of free-radicals.