Effects of 2-deoxy-d-glucose (2-DG) on radiation-induced DNA double-strand breaks (dsb) have been studied under non-growth conditions in a respiratory-deficient strain of the yeast Saccharomyces cerevisiae. Velocity sedimentation in neutral sucrose gradients was used to measure DNA dsb. Addition of 2-DG to the liquid-holding medium (67 mm phosphate buffer, pH 5, 30°C) at an equimolar concentration with glucose (50 mm) reduced the rate and extent of dsb rejoining. The inhibition of rejoining mediated by 2-DG is reversible for the majority-but not all-of the radiation-induced dsb.