The article presents issues related to weldability assessment concerning thick-walled materials used in the making of steel welded structures. The article describes weldability assessment tests in accordance with the guidelines of test SEP 1390, recommended for thick-walled structural materials exposed to dynamic loads. The objective of the tests involved the assessment of the usefulness of test SEP 1390 when evaluating the weldability of thick-walled structural materials used for welded structures.