Professor Brown is highly regarded overseas for his pioneering and extensive contributions to theoretical chemistry. Since 1948 he has developed an original approach to the quantummechanical theory of organic chemical reactions and through it has stimulated both theoretical and experimental investigations throughout the world. His work has thrown considerable light on a thoroughly neglected and most complex aspect of chemistry. In an effort to improve the understanding of the chemistry of complex organic molecules through the acquisition of further knowledge of their molecular structures and energies, he has developed a novel approach to the calculation of molecular properties based on the variation of the electro-negativity parameters. This method, known as the VESCF method, has been developed and applied to the calculation of spectroscopic intervals, electron distributions, dipole moments and ionization potentials of a number of heterocyclic compounds by Brown and his students with considerable success. In addition Brown has made significant contributions to other aspects of molecular theory.