In the course of our work within the framework of an interdisciplinary project dealing with the absolute dating of fossil
bones from Austrian caves by means of the U-series method we became interested in possible U-concentration gradients in the
bone samples. A successful attempt is reported to make the U-distribution in bones directly visible by irradiating the samples
with thermal neutrons and detecting the emitted fission products of235U in a plastic foil using the track etch method. This turns out to be possible also for relatively small U-concentrations
of the order of 1 ppm. The uranium seems to concentrate near the surfaces which is in qualitative agreement with earlier results
from the literature obtained by means of neutron activation analysis.