Low temperature operation of emitter-coupled logic circuits offers potential advantages in reliability, noise immunity, power dissipation, and speed. Experimental picosecond germanium integrated circuits exhibit significant improvements in delay with moderate cooling, in contrast to observed degradation in the performance of comparable silicon circuits. The results of a, study of the design factors and performance of germanium circuits at low temperatures are described, with comparisons to silicon. The effect of temperature on circuit propagation delay is emphasized. Brief discussions are included relating observed circuit and transistor temperature dependences to those of more fundamental parameters and processes. Copyright © 1968 by The Institute of Electrical and Electronics Engineers, Inc.