The analysis of historical. replacement of old by new technologies has shown that most of these processes can be described by simple rules that are captured in the logistic substitution model (see Marchetti, 1979; Marchetti and Nakicenovic, 1979; Nakicenovic, 1984), and that technological substitution, expressed in terms of market shares, follows characteristic S-shaped curves. In order to illustrate and describe the properties of the approach we first give examples of how new energy forms replaced their predecessors, since technological changes in the energy system constitute one of the first and most complete applications of logistic substitution analysis. To further explore this method we then describe similar substitution processes in steel production and the merchant marines.