25 Amaryllidaceae alkaloids belonging to different skeletal types were evaluated for their cytotoxic activity against one murine non-tumoral cell line (LMTK) and two human tumoral cell lines (Molt4 and HepG2) according to established protocols. Significant differences of activity related with the type of skeleton of the tested alkaloids could be observed. Pretazettine (22) was among the most active compound among the 25 tested alkaloids on the Molt4 lymphoid cells, but was inactive against HepG2 hepatoma. On the other hand, lycorenine (11) was found to be the most cytotoxic compound against HepG2 hepatoma, even though it appears to be active against Molt4 cells. Almost all of the tested alkaloids showed cytotoxic activity against fibroblastic LMTK cells. Only mesembrenone (25) showed some specificity against Molt4 cells in comparison to LMTK cells.