Hydrogen incorporation during gas-phase growth of III-V nitrides is thought to play an important role in determining the apparent doping efficiency, due to unintentional passivation of dopants. Hydrogen implantation can also be used for electrical and optical isolation of neighboring devices, as in other lll-V materials such as GaAs. We have implanted 2H at 40 keV to doses of 5 × 1015 cm-2 at room temperature into epitaxial layers of GaN, AIN and InN grown by MOMBE on GaAs substrates, and measured the ion ranges and hydrogen redistribution upon subsequent furnace annealing. The hydrogen profiles remain unchanged for annealing temperatures up to 800–900°C for GaN and AIN, and 600° for InN. Samples were also deuterated from an ECR plasma at 250 or 400°C for 30 min, producing 2H incorporation depths of ≤ 1 μ in GaN. With annealing, there is no significant hydrogen redistribution observed at temperatures up 800°C. Hydrogen concentrations remain in the range ∼ 1019 cm-3 under these conditions. At 900°C considerable hydrogen outdiffusion to the surface occurs. The thermal stability of hydrogen in these III-V nitride films indicates the need for post-growth annealing at high temperatures to achieve appreciable doping efficiencies.