The paper briefly describes a study on potential hazards of thirty products listed in the IGC code and risk assessment of the products. They are one of problems which should be solved for safety assessment of liquefied gas tankers. Some of knowledges gained are as follows ; a) All of the potential hazards could be presumably pointed out, b) State and phenomenon of the products involved can be assumed and some of simple assumption methods are proposed, c) Some of simple assumption methods are also proposed for the risk assessment, such as dangerous distance of vapour cloud, fire-explosion etc. The study is mainly based on data available for LNG, Propane and Oil products. It is desirable to be experimentally studied on Ammonia, Butane and Ethylene as typical substances, since it seems that their characteristics at dispersion into atmosphere, and evaporation and spreading onto water are different from those of LNG, Propane and Oil products.