The product of large scale high speed aluminium vessels has increased. For those vessels, reduction of structural weight becomes an important subject, and structural elements of light weight but high strength is sought for. For hull structures of aluminium ships, extrusions from A 5083 S-H 112 alloy, pi shaped sections, had been popular. However, from the view point of the lightening above mentioned, extruded hollow sections from A 6 N 01 S-T 5 alloy and pre-ribbed panels of A 5083 P-H 321/A 5083 S-H 112 were developed and are going to be applied to hull structures. In this paper, the buckling strength of hull structure by these extrusions and pre-ribbed panel is dealt with. Using these elements, test models were manufactured. Axial compression tests were performed on the models. Based on the test results, the efficiency of the elements, in saving structural weight was studied.