New cytotoxic compounds l-7 were isolated along with onnamide A (9) from a marine sponge Theonellu sp. collected at Hachijo Island, whereas another Theonelka sponge yielded 8. The structures of these compounds were determined by interpretation of the NMR spectral data as well as by comparison of spectral data with those of 9. Six compounds (l-6) were highly cytotoxic against the P388 cell line.