On Monday, April 22, 1963, some five months after the death of Niels Bohr, the American Physical Society held a special session in his memory as part of the Society's spring meeting in Washington, D.C. Four of Professor Bohr's friends and former colleagues, J. Rud Nielsen, Felix Bloch, John A. Wheeler, and Le´on Rosenfeld, were invited to participate, and articles based on their talks on that occasion are included in the following pages. The Bell Telephone Laboratories, which had originally intended to sponsor a similar tribute to be held in the New York area, cooperated in planning the Niels Bohr Memorial Session in Washington and provided for the traveling expenses of Professor Rosenfeld and of Niels Bohr's son, Aage Bohr, both of whom came to the meeting from Copenhagen.