Shimofuridins B - G (2 - 7), six new nucleoside derivatives with an acylfucopyranoside moiety, have been isolated from the Okinawan marine tunicate Aplidium multiplicatum by careful HPLC separation and their structures elucidated on the basis of spectroscopic data. During our studies on bioactive substances from Okinawan marine organisms, we recently isolated shimofuridin A (1), a nucleoside derivative containing an acylfucopyranoside moiety, from the Okinawan marine tunicate Aplidium multiplicatum Sluiter. This unique nucleoside (1) exhibited cytotoxic and antimicrobial activities and the structure including the absolute stereochemistry of all chiral centers was established by spectral and chemical means. We further continued investigation on the extract of this tunicate and careful studies on the HPLC separation of closely related analogs resulted in the isolation of six new nucleoside derivatives, shimofuridins B - G (2 - 7). This paper deals with the isolation and structure elucidation of 2 - 7. Shimofuridins B - E (2 - 5) are stereoisomers of shimofuridin A (1) as to the geometry of the double bonds in the unsaturated acyl chain moieties, while shimofuridins F (6) and G (7) possess homologous acyl chains with two more carbon units.