This meeting, Columbia University Theory Days, is a meeting which has been held twice per year, once in the fall and once in the spring, for the past twelve years. This continuing conference attracts 150 -- 200 researchers, mostly from the Metropolitan New York City Area. Each theory day consists of four one-hour invited talks, with scheduled discussion session after each talk. There are two primary goals which have been accomplished by the previous twenty-four theory days: (1) The opportunity for theoretical computer scientists to meet and exchange ideas; (2) Permit those researchers in allied areas to learn of new theoretical results and to encourage theoreticians to help solve problems in these applied areas. The mailing list contains more than 700 names of scientists, students and computer professionals with an interest in theory. The speakers of the first twenty-four theory days included such theoreticians as A. Shamir, S. Micali, M. O. Rabin, R. Karp, A. R. Meyers, J. D. Ullman, C. Papadimitriou, N. Lynch, S. Goldwasser, S. R. Kosaraju and J. Feigenbaum. The Department of Computer Science at Columbia University covered the expense of the first five years, and the department together with the National Science Foundation covered the expense of the following seven years. The National Science Foundation is providing partial support for the next six Theory Days.