Recently in this journal Schwarcz et al. (J.Hum.Evol. 35, 635-645, 1998) presented the results of gamma-ray spectrometric U-series dating of the Tabun C1 Neanderthal, assigning a date of 34±5 ka using early uptake (EU) and linear uptake (LU) models. Although application of such open system models is necessary in uranium series dating of bone because bones take up uranium after deposition, we show that simple EU and LU models are often inadequate. In many bones uptake may be recent, or leaching may have occurred. In such cases the EU and LU models can grossly over- or under-estimate the age of the bone. Given that evidence for the form of U uptake is lacking in the dating of Tabun C1, we urge that the date be regarded as potentially problematic and that it should be used with caution. (revue)