Several series of nonlactonic podophyllic aldehyde analogues were prepared and evaluated against several human tumor cell lines. They had different combinations of aldehyde, imine, amine, ester, and amide functions at C-9 and C-9' of the cyclolignan skeleton. All the compounds synthesized showed cytotoxicity levels in the microM range and below. Within the new series tested, compounds having an aldehyde or imine at C-9 and an ester at C-9' were the most potent, with GI(50) values in the nM range, some of them being several times more potent against HT-29 and A-549 carcinoma than against MB-231 melanoma cells. Cell cycle studies and analysis of the microtubule-disrupting capacity have demonstrated the existence of two different mechanisms of cell death induction for compounds with closely related structures.