Phenolic compounds are prevalent as toxins or environmental pollutants, but they are also widely used as drugs for various purpose including anticancer agent. A novel biphenolic compound, bis(2-hydroxy-3-tert-butyl-5-methylphenyl)methane (GERI-BP002-A) was isolated from the fermentation broth of Aspergillus fumigatus F93 previously, and it has revealed cytotoxicity against human solid tumor cells. Its effective doses that cause 50% inhibition of cell growth in vitro against non-small cell lung cancer cell A549, ovarian cancer cell SK-OV-3, skin cancer cell SK-MEL-2 and central nerve system cancer cell XF498 were 8.24, 10.60, 8.83, 9.85 μg/ml respectively. GERI-BP002-A has also revealed cytotoxicity against P-glycoprotein-expressed human colon cancer cell HCT15 and its multidrug-resistant subline HCT15/CL02, and its cytotoxicity was not affected by P-glycoprotein. We have also tested cytotoxicities of structurally related compounds of GERI-BP002-A such as diphenylmethane, 1,1-bis(3,4-dimethylphenyl)ethane, 2,2-diphenylpropane, 2-benzylpyridine, 3-benzylpyridine, 4,4′-di-tert-butylphenyl, bibenzyl, 2,2′-dimethylbibenzyl, cis-stilbene, trans-stilbene, 3-tert-butyl-4-hydroxy-5-methylphenylsulfide, sulfadiazine and sulfisomidine for studying of structure and activity relationship, and from these data we could suppose that hydroxyl group of GERI-BP002-A conducted important role in its cytotoxicity.