Although the neurotoxicity of CS2 has been recognized for over a century, presently there is no accepted biomarker of effect for CS2 exposure. Previous investigations have supported covalent cross-linking of erythrocyte spectrin as a potential preneurotoxic marker reflective of the biochemical changes occurring within the axon. In the present investigation, the potential of using CS2 promoted modification of hemoglobin as a dosimeter for quantifying exposure to CS2 was evaluated. Liquid chromatography was used to isolate and measure alpha and beta chains of globin in blood obtained from rats exposed to CS2 by inhalation as a function of exposure level and duration. The degree of globin modification was compared to light microscopic and ultrastructural changes in the central and peripheral nervous systems to determine the temporal relationship of globin modification to the structural changes in the axon. Samples obtained from rats exposed to CS2 contained a globin chain not present in control samples. Analysis of the peak corresponding to the new chain using electrospray mass spectrometry was consistent with the generation of a single dithiocarbamate ester or thiourea intramolecular cross-link in the alpha 1 major chain. This altered globin chain was detectable both at the subneurotoxic level of exposure and prior to axonal structural changes at the neurotoxic levels of exposure used. The extent of modification was positively correlated to the exposure level and duration for all conditions examined. These findings support hemoglobin as a potential preneurotoxic biomarker of effect for CS2 possessing several practical advantages relative to the use of CS2-mediated spectrin cross-linking.