In order to understand migratory history of Japanese eel Anguilla japonica, otolith of 29 eel specimens collected in 3 sites in the coast of Tokushima prefecture were extracted for X-ray microprobe analysis. The line analysis of Sr:Ca ratios along the life history transet of each otolith showed a peak (ca 12 - 15 x 10 exponent -3), which corresponded to the period of their leptocephalus and early glass eel stage in the ocean. The mean Sr:Ca ratios from the elver mark to the otolith edge indicated that there were 3 catergories of migratory history. River eels which entered and remained in freshwater river habitats after arrival in the estuary, the mean Sr:Ca ratios were 1.32 +/- 0.30. Estuarine eels which inhabited estuaries or switched between different habitat, the mean Sr:Ca ratios were 4.63 +/- 1.21 and Sea eels which spent most of their life in the sea and did not enter freshwater, the mean Sr:Ca ratios were 7.20 +/- 0.59. The results suggested that Japanese eels did not obligate to migrate to freshwater after recruiting to coastal areas, they could reside in brackish or sea waters until fasting spawning migration.