The effects of seven compounds 1-7, isolated from a tropical ascidian Lissoclinum cf. badium, on IL-8 production in PMA-stimulated HL-60 cells were examined. Lissoclibadins 2 (2) and 3 (3) and lissoclinotoxin F (5) increased the IL-8 production in a dose-dependent manner. Compounds 2 and 5 are structural isomers possessing dimeric structures of trans and cis-orientations, respectively, and showed a very similar activity on the induction of IL-8 levels. Compound 3 and lissoclinotoxin E (4) are also structural isomers having dimeric trans and cis-structures, respectively, but 4 did not induce the IL-8 production. Lissoclibadin 1 (1, trimeric compound) and two monomeric compounds (6 and 7) did not increase the IL-8 level. Therefore, the differences in their structures remarkably affected the IL-8 production activity, the inhibition of cell proliferation, and the survival of HL-60 cells. Lissoclibadin 2 was the most interesting compound of the seven metabolites tested in this study.