One hundred twenty-five Chernobyl accident recovery workers (liquidators) who were exposed to low-dose radiation were studied over a period of 4-6 years for changes in levels of hormones, arachidonic acid metabolites and cyclic nucleotides. Some significant changes were observed, especially in the levels of metabolites that are regulators of cell functions. In comparison to controls, there were increased levels of thyroxin, cortisol, thromboxane B2, and immunoglobulins G, A and M, and reduced levels of growth hormone, cyclic nucleotides and 6-keto-prostaglandin F1. The degree or presence of these metabolite imbalances did not correlate with the level of the radiation dose received. The only change found that did relate to the radiation dose received was a statistically significant increase in levels of biomarkers for oxidative stress, seen in workers who received higher doses.