This volume forms a permanent record of lectures given at the International Conference on Spectral Theory of Differential Operators held at the University of Alabama in Birmingham March 26-28, 1981.
The conference was supported by about 90 mathematicians from North America and Europe. Its main purpose was to provide a forum for the discussion of recent work in certain areas of the theory of ordinary and partial differential equations loosely connected under the general heading of Spectral Theory. Invited one-hour plenary lectures were given by F. V. Atkinson, who gave a series of three lectures, P. Deift, \~. N. Everitt, H. Ka If, T. Kato, R. M. Kauffman, M. Schechter and B. Simon. The remainder of the programme consisted of invited special session lectures, each of one-half hour duration.