Dramatic advances have been made in the last few years in our ability to study the behavior of single macromolecules. These new experiments require sopisticated applications of cutting-edge technologies and the development of new theoretical approaches to interpret them so as to extract the maximum possible microscopic information. This has recently become the main focus of our research.In this reporting period, four papers papers dealing with the following topics appeared in print: (1) The development of an analytic theory for the current at ultramicroelectrodes. The predictions of this theory were compared with experimental results obtained using elliptical electordes obtained in the laboratory of Mark Wightman at the University of North Carolina (2) The general theory of photon counting in single-molecule spectroscopy ( specifically the statistics of transitions in an arbitratry kinetic scheme) was developped and applied to the the analysis of experiments on single molecule enzyme catalysis perfomed in the laborastory of Sunney Xie at Harvard. (3) A novel theory was developped to extract kinetic information ( specifically the intrinsic rates and free energies of activation) from single molecule pulling experiments performed using optical tweezers and atomic force microscopes. This complements the work reported last year dealing with the protocal of obtaining equilibrium free energy surfaces from single molecule force spectroscopy (4) The theory of photon counting histograms for molecules that diffuse in and out of the laser beam was formulated for the first time . Such histograms contain information about the nature of conformational changes of the fluorophores. The last three of these papers represent a significant advance in our ability to interpret single-molecule force and fluorescence spectroscopic experiments.