The paper reports on HICASS-H, a computer aided system for hull structure design, which is developed as a subsystem of previously presented HICASS. The system deals with consistently the hull structural information ranging from design to production line. The operation starts with lines fairing and is followed by definition of seams and longitudinals on the shell then successively by disposition of internal hull structures. Most of data, input or generated during these operations, are kept in/taken out of the data base which is one of the key elements of the system. So as to support this, a number of commands, in the form of usual terms, are provided for the convenience of communication between designers and the data base. With a view to the fact that the design process is subjected to fairly frequent trial and error and that the data increase and become full gradually as the design proceeds, the data base is so schemed as to face up to such circumstances. Various drawings are taken out of the data base at designer's option. It is also utilized for the development calculation of various curved surfaces as well as the manipulation of NC data including those of the secondary members such as brackets, stiffeners etc.