This report describes the results of the international comparison EUROMET.M.M-S1 (also known as Eurmet Project No. 461) between 15 participants. The comparison started in June 2001 and finished in July 2003. Czech Metrology Institute was the pilot laboratory of the project. The transfer standard with nominal mass of 500 kg was provided by Raute Precision (Finland). Agreement between all participants is good except one laboratory. The result of the laboratory was stated as an outlier and was not used for calulating of the reference value.