Perovskite SrRuO3 films are promising candidates as metallic electrodes in high-permittivity (high k) capacitors and possibly in fully epitaxial CMOS stacks. The thermal stability of SrRuO3 during forming-gas (FG) anneal is an important requirement and is investigated here by in situ X-ray diffraction (XRD) and electrical resistivity measurements. A weak and smooth increase of the resistivity is observed above 300 degreesC and is attributed to the effect of hydrogen diffusion. It is followed by a sharp transition at 500 degreesC into a highly resistive state due to the decomposition of the SrRuO3. We found that the addition of about 1% O-2 in the FG prevents both the onset of resistivity at 300degreesC and the decomposition of the oxide.