[en] Base damage and phosphate release have been determined simultaneously from gamma irradiated aqueous solutions of DNA in O₂ and N₂. Base damage (bd) was determined by the decrease in optical density at 255 nm in a Cary 14 spectrophotometer. Inorganic phosphate (Psub(i)) was estimated by a modified Berenblum and Chain method. Gamma irradiation was from a Co-60 gamma cell at a dose rate of 4 krad/min and upto a total dose of 320 krad. DNA solutions used were in the concentration range of 20 μg/ml to 200 μg/ml of salmon sperm DNA in neutral aqueous solution. An inverse correlation was found between bd and Psub(i) for all concentrations of DNA. This was seen both in O₂ and N₂. Oxygen enhancement ratio (defined as ratio of yield in O₂ to that in N₂) was more than 1 for bd and at corresponding doses OER for Psub(i) was less than 1. The OER value for Psub(i) changes at higher doses where bd gets saturated. These results show that there is a competition for radiation produced damaging species, between these two sites (viz. base and sugar-phosphate parts of DNA molecule). In general Psub(i) released was about 10% of bd for a given dose both in O₂ and N₂. (author)