We show that the near surface structure of lamellar ABC triblock copolymer mesostructurescan deviate considerably from the “ideal” surface anticipated from the bulk structure of the material.Varying the molecular architecture and the surface energy difference between the respective blocks, weshow that such surface reconstructions are caused by a complex balance of enthalpic and entropiccontributions to the free energy of the system. The results are compared to the well-known surface behaviorof classical crystals and experimental conditions for what may be called “block copolymer surface science”are discussed.