The importance of dynamic strength characteristics of LNG cargo containment system, various research efforts including dry-drop and wet-drop tests as well as sloshing test have been carried out by GTT, shipyards, oil companies, universities as well as classification societies. However, no explicit consideration with regard to the structural performance of insulation system toward the cryogenic environment is yet given. Besides only limited information regarding experimental procedure and analysis results is shared among stakeholders, and it acts as obstacles for the development of consistent CCS (Cargo Containment System) design criteria in an effective manner. Demand for LNG carriers with increased capacity requires further development of the design technology for LNG cargo tanks to meet the safety requirements due to the larger size LNG tanks. In this study, a systematic experimental research is required for the assessment of fatigue strength at cryogenic environment as well as impact strength of insulation system. The different sized mastic support has been adopted to compare the cryogenic fatigue performance. One of the main challenges in this work is to generalize the test results for use in case of other mastic support sizes. The aim of the study is to investigate the typical failure mode and obtain the S-N data under cryogenic fatigue loading. This study will be used as a fundamental study for the cryogenic fatigue assessment for the LNGC insulation system as well as a design guideline. The fatigue tests of Mark-III insulation system are carried out at room temperature and cryogenic temperature, and considered sloshing effect (R = −10). The load levels have been determined based on ultimate strength of reinforced polyurethane foam 12.2bar.Copyright © 2009 by ASME