The cytotoxicity, hydrophobicity (log P), cellular uptake, aqueous reactivity, and extent of DNA adduct formation in the A2780 ovarian carcinoma cells for four osmium(II) arene complexes [(eta(6)-arene)Os(4-methyl-picolinate)Cl] that differ only in their arene ligands as benzene (1), p-cymene (2), biphenyl (3), or tetrahydroanthracene (4) are reported. There is a correlation between hydrophobicity (log P), cellular uptake, nucleus uptake, and cytotoxicity of the complexes, following the order 3 approximately 4 > 2 > 1, suggesting that the arene plays an important role in the biological activity of these types of compounds. Cell distribution studies using fractionation showed that all four compounds distribute similarly within cells. DNA binding of osmium did not correlate with cytotoxicity, indicating that the nature of the DNA lesion may also be crucial to activity. TEM images of ovarian cells treated with 3 revealed morphological changes associated with apoptosis with possible involvement of mitochondria.