A steady planar detonation wave, considered to be a shock wave followed by a reaction zone, is studied with both irreversible and reversible first‐order reaction kinetics. A perturbation solution with first‐order transport effects, valid in the reaction zone for those cases where the ratio of the characteristic collision time to the characteristic chemical time is small compared to one, is presented with sample calculations of temperature and concentration distributions for typical irreversible and reversible reaction cases. Analysis of the solution shows that simple series solutions and hence the given perturbation solutions do not hold near the hot boundary for all possible final Mach numbers. In the irreversible reaction case, the perturbation solution is a valid approximation for final Mach numbers less than (1 −B)½, whereBis the ratio of characteristic times, the approximation becoming less accurate as the Mach numbers tend toward this limiting value. In the reversible reaction case, the perturbation solution is a valid approximation for final Mach numbers up to the Chapman‐Jouguet value of unity, if the Mach number is based on the equilibrium speed of sound.