The pentacyclic triterpene glycyrrhetinic acid is an interesting natural product exhibiting various biological activities. Especially its ability to induce apoptosis in tumor cells is of high scientific interest. In this study we altered the lipophilicity in ring A by derivatization at positions C-2 and C-3. The consequences of these variations on the cytotoxicity were investigated applying a colorimetric sulforhodamine B assay using 8 different human tumor cell lines. An acridine orange/ethidium bromide (AO/EB) test and a trypan blue test were used to determine the extent of apoptotic activity of some of these compounds