-A family of novel Josephson logic circuits called current injection logic (CIL) is presented. In contrast to previous approaches, it combines magnetically coupled interferometers with novel nonlinear, injection gates to obtain ultra-fast logic speeds, wide margins, and greater fan-in and fan-out capabilities. Fastest logic delay of 30 ps/gate is measured averaged over two-and four-input OR and AND gates (average fan-in = 4.5, average fan-out = 2.5) fabricated using 2.5 µm nominal design rules. The average power dissipation of these experimental circuits is 6 µW/gate. an unprecedented logic delay of 13 ps/stage is measured on a chain of two-input OR gates, and the logic delay for a circuit consisting of two two-input OR gates, the outputs of which are “AND”ed, is measured at 26 ps. The experimental results are found to be in excellent agreement with delay estimates based upon computer simulations. Copyright © 1979 by The Institute of Electrical and Electronics Engineers, Inc.