The xylidide 2,6‐dimethylaniline (2,6‐DMA) has produced carcinomas and papillary adenomas in the nasal cavity of rats at high dietary doses (3000 ppm) in a 2‐yr bioassay. The objective of the present study was to measure the covalent binding of 2,6‐DMA to DNA of rat ethmoid turbinate tissues and, for comparison, to DNA of rat liver. The potent hepatocarcinogen 2‐acetylaminofluorene (AAF) was studied as a positive control for adduct formation and covalent binding index (CBI) calculation. Both 2,6‐DMA and AAF were administered as14C‐(ring)‐labeled agents to naive rats and to rats pre‐treated for 9 d with unlabeled 2,6‐DMA or AAF.