The main objective of genetic monitoring in human health surveillance is to prevent excessive exposure to genotoxic agents and to ensure the safety of the exposed or potentially-exposed populace. To attain fully this objective one must understand low dose exposure and associated effects so as to relate both to long-term health consequences. Experience with radiation has provided the most precise knowledge of the dose-effect relationship, and it is that knowledge that the authors wish to exploit in the present investigation. Over the past few years the laboratory has implemented and further developed several methods for cytogenetic and mutational testing and monitoring. These methods employ periphral blood lymphocytes and fibroblasts to detect chromosomal structural aberrations, sister-chromatid exchanges, and gene mutation at specific genetic loci.