Transverse wave spacings have been measured for self-sustaining detonations in mixtures containing oxygen plus diluents and either hydrogen, methane, acetylene, or ethylene as fuel. These spacings are compared to induction and recombination zone lengths calculated for an equivalent CJ one-dimensional detonation in the hydrogen system and to calculated induction zone lengths in the other systems. The results suggest that for high dilutions the induction zone lengths are controlling the spacing, whereas at low dilution (and therefore highdetonation temperatures) recombination zone lengths become the important chemical effect in determining spacing. © 1969 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.