Here we briefly review some nontraditional theoretical views developed in this group on acid-base proton transfer (PT) reactions AH(...)B-->4A(-...)HB(+) in solution, whose key ingredients are inclusion of the quantum character of the proton motion, the identification of a solvent coordinate as the reaction coordinate, and attention to the AB hydrogen bond in the reacting pair. The reaction rate constant is discussed in two separate quantum regimes, which we term 'adiabatic' and 'nonadiabatic', with attention given to consequences for free energy relations (FER) and kinetic isotope effects (KIEs). (C) 2003 Elsevier B.V. All rights reserved.