The spawning behavior of the puffer Fugu niphobles was observed at Fukiage Beach, Aikawa Town on Sado Island in the Sea of Japan during its reproductive season in 1978 and 1979.The spawning beds, consisting of gravel, pebbles and boulders, were some-what influenced by underground water coming from the paddy-field located on a coastal terrace just behind this beach.The spawning season lasted for more than a month from early June to late July.The spawning occurred almost every evening during a period of fifty minutes before and after sunset.It is remarkable that at Fukiage Beach spawnings show a weak and rather vague lunar periodicity.Males outnumber females in and near the spawning beds.It is estimated, on the basis of gonadal index and histological examination of both sexes, that the peak of maturation is in early June in the male and in late June in the female, although the highest frequency of spawning behavior was not seen until early July.Furthermore, false spawnings were noticed toward the end of the spawning season.