AbstractA brief review of recent developments in the theory of unimolecular reactions is presented, with emphasis on the work carried out at The University of Chicago. The subjects considered are: the development of a paradigm for the control of selectivity of a photoinduced reaction; the development of an alternative form for the classical mechanical theory of the rate of a unimolecular reaction; the beginnings of an understanding of the influence of classical mechanical chaos on the corresponding quantum‐mechanical description of an unbounded system; and the possible decoupling of a part of anN‐degree‐of‐freedom system from the rest of the system on a time scale of interest with respect to subsystem internal energy transfer and chemical reaction. The intellectual linkages between these subjects are very briefly s