U concentrations were measured in the enamel and the dentine of 5 bovid teeth obtained from Olduvai Gorge, Tanzania. Their ages were estimated on the basis of their association with Olduvai Beds I through III/IV which in turn, were estimated from ₁₄C, paleomagnetic, fission track, K-Ar, and amino acid data. Analyses for U were made by fission track counting. Analysis of CaO, P₂O₅, Na₂O, MgO BaO and Al₂O₃ was made using an electron microprobe and the data are reported. The fossilized teeth were found to contain U concentrations up to 200 times higher than occur in common igneous and metamorphic rocks and to range as high as 700 ppm. Unfossilized bovid teeth were estimated to contain less than 0.02 ppm U. Thus it is likely that the specimens studied formed with low concentrations of U and that the bulk of the U now in the teeth was introduced during fossilization. An explanation is hypothesized.