A samples storage system for pharmaceutical development in which the usable volumes of ultramicrotubes (384 tubes) are increased and smooth insertion and extraction of ultramicrotubes is possible irrespective of the positions of the ultramicrotubes. The samples storage system includes tubes in which samples are sealed and a storage rack for vertically accommodating a plurality of the tubes in a grid pattern. Each tube is of a rectangular hollow tubular cross-section and the intersect is tapered toward the bottom portion of the tube. Corner portions of the outer four side surfaces of the tubes are chamfered. The storage rack has engagement partition walls forming open-ended sections in a grid pattern inside the rack frame. The height of the walls is smaller than the length of the tube, and tube-supporting pins project vertically from the intersections of the grid. The outermost walls of the grid are spaced inwardly from the frame so that all of the tubes in the grid are supported for ready insertion and removal.