The recent trend in the automotive industry toward improved safety and reduced weight has led to the increased use of high strength steels in parts that were formerly made of mild steel. As part of an evolutionary substitution technology, it is necessary to evaluate as critically as possible the components where high strength steels are most effective. This paper presents a methodology to predict the potential for thickness reduction when using high strength steels in fatigue critical applications. With the growing emphasis on the finite-life design concepts, the methodology makes use of strain-life parameters for predicting thickness reduction. The role of stress concentration at notches is also highlighted. The methodology is illustrated with data for several hot-rolled, cold-rolled, and galvanized high strength steels.