A method for the determination of Cr in biological materials with high accuracy is reported for use as an independent reference method. It is based on radiochemical neutron activation analysis (RNAA) in combination with an individual yield determination based on the online yield principle. A precision of better than 4% between replicate determinations was achieved by application to biological materials with Cr contents on the 100 lag. kg- 1 level. Analytical characteristics of the method offer good perspectives for Cr assays at lower levels.