These volumes contain most of the papers presented during the scientific sessions of the Sixteenth General Assembly of URSI in August 1969. The programs were arranged by the chairmen of the respective URSI Commissions during the period 1966–1969. The chairmen of the Commissions responsible for the papers were: volume 1, C. O. Hines, H. G. Booker, and F. Horner; volume 2, J. A. Saxton, E. J. Blum, and L. Essen; volume 3, F. L. Stumpers and P. Grivet. Each volume costs $5.00 (250 Belgian francs) per copy, surface postage included. The three volumes ordered simultaneously cost $12.00 (600 Belgian francs). Copies can be sent air mail by arrangement, for an additional charge.