Studies have been made at 500°C of the second limit, and of the induction period and maximum rate of the slow reaction, of D2+ O2+ N2 mixtures in aged boric-acid-coated vessels. The results enable the velocity constant ratios k11D/k½10D, k8D/k2Dk½10D, k14D/k2D and k15D/k1D, to be evaluated. From a comparison of the rates and peroxide concentrations in the hydrogen and deuterium systems, a value of k7 D can be obtained.