The aim followed in the present study was to investigate the economic aspects of , and to derive Economic Weights (EWs) for Mature Body Weight (MBW) as well as for age at First Calving (AFC) in Holstein dairy cattle of Iran. Economic values (EVs) for traits were estimated using trait-by-trait bio-economic models. Absolute EVs were RLs -16400 and -17900 per cow per year for MBW and AFC, respectively. Because of the negative effects of these traits on profitability, EWs of -7540 for MBW and -3760 for AFC are suggested for a national selection index. A one day increase in AFC increased production costs by Rls 39600 per cow per year. Sensitivity analysis revealed that the EV for MBW was more sensitive to changes in live weight price than to feed costs. Results obtained in this study can be used in the development of breeding objectives and in the cost- benefit analysis of management programs which aim at changing the attitudes of farmers and of their consultants towards decreasing costs and therefore increasing profitability.