X ray computed tomography CT was used to observe nondestructively the internal structure of sea ice grown in the laboratory. The CT images were compared with photographs taken by the conventional method. Both brine layers and brine drainage channels, which are characteristic sea ice features, were clearly recognizable on the CT images. The CT scanner is an extremely useful tool for examinations of sea ice structure and can possibly be applied to three-dimensional measurements of ice core density. ¿ American Geophysical Union 1988