The objective of this study was to investigate the relation of formation of non-volatile amines to spoilage of sea foods. The amounts of six non-volatile amines, histamine (His.), cadaverine (Cad.), putrescine (Put.), spermidine (Spd.), tyramine (Tyr.) and agmatine (Agm.), formed during the putrefaction were investigated, by using the muscle of various commercial sea foods. And then, the pH value and the volatile base nitrogen (VBN) contents were investigated simultaneously. Raw pacific mackerel, tuna, sardin, pacific saury, shortneck clam and boiled octopus were allowed to stand at the room temperature of 27±2°C. The analytical methods used for the determination involved the separation of non-volatile amines from sea foods by eluting through a cation-exchange resin column, the formation of their dansyl chloride or 4-fluoro-7-nitrobenzo-furazan (NBD-F) derivatives and the determination of these derivatives by high performance liquid chromatography with a fluorescene spectromonitor. The variation of pH value was found in various sea foods during the putrefaction. And, the development of VBN contents was found to be larger in quantity in tuna, octopus and pacific mackerel than others. On the other hand, when no detectable decomposition was observed by the determination of pH value and VBN contents, various non-volatile amines, His., Cad., Tyr. and Put. have already appeared. The formation of His. was observed as decomposition of pacific mackerel, tuna and sardine progressed. Particulary, its formation in pacific mackerel and tuna went up very rapidly to a higher level than either of the other amines. The large and rapid formation and the loss of Put. were also observed during the decomposition process in octopus. Therefore, these amines may serve as quality indicators of any sea food.