Estimations of the brooding and larval developmental periods of the callianassid ghost shrimp, Callianassa japonicu Ortmann (Decapoda: Thalassinidea), under field conditions, were made on an intertidal sandflat in western Kyushu, Japan, during the breeding seasons (June-October) of 1992–1994. Females bearing eyed embryos were able to deposit a further batch of eggs 1–5 d after releasing larvae, and it is concluded that such egg deposition was preceded immediately by mating. Based on rearing experiments carried out in the field, the brooding period was found to occupy between 13 and 22 d during June to October, at pore water temperatures of 20.5-27.5°C and salinities of 33.0–34–5‰, a shorter period than those reported for seven other callianassid species. Based on temporal changes in the densities of larvae released by females and newly-settled juveniles on the sandflat, time-lags between the release and settlement events suggested the period of planktonic development with six zoeal stages and the 1st post-larval stage to range from 20 to 25 d during mid-June to mid-August, at water temperatures of 18.5-24.5°C and salinities of 32.0–35.0‰. This is the second shortest larval period among those reported for seven other callianassid species that have five or six zoeal stages.