Seven species of the estracod superfamily Cytheroldea and four species of the superfamily Darwinuloidea were recovered firom Lake Biwa in west-central Japan. Four of the cytheroidean species are newly described herein, all belonging to the genus Limnoqythere: L, katniyai sp, nov., L, fude sp, nov., L. gevigatus sp, nov,, and L. mphotna sp, nov. Two ethers are new records for Lake Biwa, namely Limnoaythere stationis Vavra, 1891 and Migtampris digitifornzis Smith and Hiruta, 2004, The four newly described Limnoc;ythere species may be an exarnple of a small endemic speeies flock. Ofthe Darwinuloidea recovered, two species, Darwinula stevensoni (Brady and Robertson, 1870) and Vbstagenula sp., have been previously recorded from the lake. Vestalenula sp. is herein identified as V aylindrica (Straub, 1952), which was previously known only as a ibssil firom Europe and the Middle East: this is the first report of a living populatton. The two other darwinulid species, also belonging to the genus Vlastalenula, are new records for Japan, namely Vbstalenula lundi (Neale and Victor, 1978) and U molopoensis (Martens and Rossetti, 1997). Their discovery in Lake Biwa dramatically extends the known distribution of all three Vlestalenula species by thousand$ of kilometers and increases the number of darwinulids known in Japan from three to five.