Unscheduled DNA synthesis (UDS) was examined in normal human peripheral blood lymphocytes (HPBL) exposed to n- and tert.-butyl glycidyl ethers (BGE). n-BGE, which is currently used as a major reactive diluent for industrial epoxy resin systems, has been implicated as a bacterial mutagen. t-BGE, a potential replacement for n-BGE, is less cytotoxic to HPBL. Both these BGEs have demonstrated genetic activity in human cells. Here, slide autoradiography and liquid scintillation counting techniques have been used to show that both n-BGE and t-BGE induce repair-DNA synthesis in normal HPBL. These agents demonstrate similar dose-response relationships over the range of concentrations up to 333 micrograms/ml. Cultures were examined for repair-DNA synthesis after a continuous 5-h exposure to varying concentration of n-BGE or t-BGE.