This analysis allowed us to address two essential points: (1) to confirm that all B-CLL samples were partially or totally resistant to anti-CD95 or rTRAIL treatments, accordingly to data reported in the literature previously (MacFarlane et al, 2002, 2005); (2) to establish the correct range of quercetin concentrations to avoid cytotoxic doses of quercetin that could mask the ability of the molecule to sensitise B-CLL cells to DR-dependent apoptosis. Here, FAS is linked to B-cell chronic lymphocytic leukemia.