In this paper a summary of results is presented of full scale measurements on a LPG carrier of semi-membrane tank type which have been carried out for about two years during her voyage between Japan and the Persian Gulf. The unmanned measurements have been made on dynamic loads caused by liquid sloshing in a LPG tank of a restricted cargo filling ratio of either over 90% or below 30%. The test includes also measurements of reaction forces acting on a tank dome supporting the tank at upper deck structure. Long term measurements of ship notion as well as stresses due to longitudinal bending of hull girder have also been carried out. A statistical study has been made on a relationship between the ship motion and the frequency of occurrence of the liquid sloshing in LPG tank. The results of the measurements have been compared with results of bench test on liquid sloshing in model tank in order to investigate into the effect of tank size on the magnitude of impact load due to sloshing.