We present results of plasma afterglow experiments on ternary electron ion recombination rate coefficients of H-3(+) and D-3(+) ions at temperatures from 50 to 300 K and compare them to possible three body reaction mechanisms Resonant electron capture into H-3* Rydberg states is likely to be the first step in the ternary recombination, rather than third-body-assisted capture. Subsequent interactions of the Rydberg molecules with ambient neutral and charged particles provide the rate-limiting step that completes the recombination. A semiquantitative model is proposed that reconciles several previously discrepant experimental observations. A rigorous treatment of the problem will require additional theoretical work and experimental investigations.