The relative effective resonance integral of U238 has been measured as a function of temperature for uranium and UO2 cylinders, 0.986 and 0.973 cm diam, respectively. The Doppler coefficients α and β are defined by: RIo refers to the effective resonance integral (excluding 1/υ absorption) at 20°C, and to and To are 20°C and 293°K respectively. The measurements utilized the activation technique in which the induced Np239 activity of a uranium bearing specimen was determined as a function of specimen temperature during irradiation. Measured values for α and β corrected for thermal expansion, 1/υ absorption, fission activity and a deviation from a 1 /E epithermal flux are for metal α = 1.14 ± 0.07 × 10 -4/oC, β = 0.53 ± 0.03 × 10-2/(°K)1/2 and for oxide α = 1.34 ± 0.11 × 10-4/°C, β = 0.69 ± 0.06 × 10-2/ (°K)1/2. The temperature increments for which these values have been obtained were 580 and 950°C for uranium metal and oxide respectively. The results presented in this report are considered to be consistent with the results of other experiments in which the activation technique was used but are lower than theoretical predictions given by Nordheim and Rosén.