The resistivity of palladium and palladium–hydrogen alloys has been studied in the temperature range 2–300 °K. At low temperatures (10 °K < T < 60 °K), it is found that ρ₁ is proportional to Tⁿ with n = 3.1 for pure palladium; but n decreases to 2.3 for an alloy with H/Pd = 0.25. For high concentrations and at low temperatures, the resistivity is found to be dependent upon the time and rate of cooling through the transformation. The residual resistivity is lower for faster cooling rates.The increase in resistivity due to 1 at. % hydrogen in palladium is calculated and found to be of the same order of magnitude as that for interstitials in other f.c.c. metals, but less then that found for hydrogen in the b.c.c. transition metals tantalum and niobium at room temperature.