The preparation of certified rapeseed reference materials and the steps taken to establish the certified values for total glucosinolate contents are described. Details are given of the studies to demonstrate the homogeneity and stability of the material. The results of the certification exercise for total glucosinolate content, which involved European laboratories who applied a variety of methods (high-pressure liquid chromatography, gas liquid chromatography, determination of enzymatically released glucose and sulphate), are presented and discussed. The certified values for the glucosinolate content (mumol/g of non-defatted whole seeds) and the 95% confidence level are the following: CRM 366 (12.1 +/- 0.8 mumol/g), CRM 190 (25.5 +/- 0.9 mumol/g) and CRM 367 (102.4 +/- 3 mumol/g) (CRM = certified reference material). Indicative values (not certified) for individual glucosinolates are also given. Certified sulphur values (mg/g of non defatted whole seeds) have been determined by other laboratories: CRM 366 (3.41 +/- 0.12 mg/g), CRM 190 (4.93 +/- 0.15 mg/g) and CRM 367 (10.5 +/- 0.40 mg/g).