Double-stranded DNA from calf thymus was irradiated in the presence of bovine serum albumin (BSA) with a ratio of 1:10 in weight, at pH7 and pH5, under aerobic and under anaerobic conditions. The irradiated biomolecules were separated by high-performance liquid-gel permeation chromatography. At pH 7, in the presence of the protein, degradation of DNA was enhanced by oxygen, while under anaerobic conditions formation of protein-DNA crosslinks was observed. At pH5, crosslinking of BSA to DNA occurred under anaerobic as well as under aerobic conditions, while fragmentation of DNA could not be detected with this method with doses up to 1600 Gy. Under nitrogen, the degradation of BSA was not altered by the addition of DNA, but in the presence of oxygen less BSA was lost for a given dose when DNA was present.