The spontaneous bilateral asymmetry was analyzed in the hermaphroditic fish Rivulus marmoratus to obtain base line data on the developmental stability of this fish. The results obtained were as follows; 1. Eight kinds of countable anatomical characters except numbers of otolith and radii branchiostegi showed bilateral asymmetry at the frequency ranging from 9.8% to 64.7%. 2. Asymmetry index was not significantly different from that of gonochoristic fish species previously reported. Genetical implication of the results was discussed in relation to developmental stability and homozygosity of this species.