Economic weights for carcass traits of 5333 Japanese Black steers each month were derived from April 1988 to December 1990 by multiple regression analysis. The carcass traits considered were marbling score (EMS No.), rib-eye area, rib thickness and subcutaneous fat thickness. Two economic variables were adopted as aggregate genotype (i.e. breeding objectives): carcass unit price (yen/kg carcass) and carcass sale price (yen/head). The economic weight for marbling score increased from 1988 to 1990, indicating that the relative economic importance of marbling score increased during the 3 years in Japan. Correlations among two indices calculated from different economic weights (i.e. a maximum value versus a minimum value of each trait) were very high, whichever economic variable was adopted.