Two groups of Japanese eel (Anguilla japonica) larvae, hatched from hormone-induced spawned eggs, were used to test the salinity tolerance without acclimation. For the first group, larvae were reared at the salinities of 15 ~ 35 ppt indoors with light intensities below 320 lux. The survival rate of larvae was highest (63.3%) for 7-d-old larvae at a salinity of 20 ppt. For the second group, larvae were reared at 0 ~ 20 ppt salinities indoors with a similar light intensity as group 1 and in a dark room with light intensities below 13 lux, respectively. In the second group, larvae died within 2 d in 0 ppt, but all larvae in 10 ppt had the highest survival rate that the 9-d-old larvae reached 76.7% indoors and 63.3% in the dark room; survival rates of 9-d-old larvae between indoor and dark-room did not significantly differ. Eye pigmentation and the demersal habit of larvae occurred from day 6.