Conventional methods for measuring ice bulk density do not allow one to detect three-dimensional changes in density in a nondestructive manner. An X ray computed tomography (CT scanner) was used to determine ice core density. This scanner has led to remarkable achievements in the field of medical science to obtain a nondestructive cross-sectional representation of the human body. In this paper the relation between density and the CT value ordinarily obtained by the CT scanner is discussed for the ice/air mixtures similar to ice core samples. The influence of impurities on the density determination is also considered. Images, taken at intervals of 2 mm, detected the internal air bubble distribution of an ice core. Three-dimensional density distribution was also evaluated on the volume elements with dimensions of 1.1 by 1.1 by 2 mm. Results of CT scanner measurements were compared with those of the conventional hydrostatic method. Comparisons made on compressed ice samples with various densities showed close agreement. The results show that the CT scanner can be used to nondestructively determine the three-dimensional distribution of ice core density and that the CT scanner is an extremely valuable tool for making detailed measurements of spatial variation in density of ice cores as well as for examining the internal structure. ¿ American Geophysical Union 1990