The papers in this session are devoted to physical chemistry and biological chemistry. Physical chemistry and the physical part of biological chemistry are areas in which computational quantum chemistry has so far had relatively little impact. This is certainly not because there are not important questions to be answered. The area of interactions between molecules or parts of the same molecule, and rotational barriers in polymer molecules, could in principle benefit from quantum mechanical calculations. The problem is rather that the interactions of interest in physical chemistry are relatively weak, ranging for the most part from.002 k cal/mole (the interaction of two helium atoms at the van der Waals minimum) to about 10 k cal/mole (a strong hydrogen bond, or a rotational barrier in a polymer molecule).