Beef cow managers annually face the question of which animals to cull from the herd and replace. The results of this decision affect not only current revenues, but, by altering the genetic composition of the herd, also affect the future profitability of the herd. These genetic changes of the herd may, therefore, be represented as a form of endogenous technological progress to the cow calf producer. This article derives general asset replacement criteria for assets undergoing either exogenous or endogenous progress and illustrates their application with a Florida cow herd example.