Reactions of 2-hydroxy-3-methoxy, 2-hydroxy-4-methoxy-benzaldehyde with 3- and 4-methoxy-substituted salicylaidehyde S-methyl-thiosemicarbazones in the presence of FeCl3 and NiCl2 resulted in the corresponding methoxy-substituted N-1,N-4-diarylidene-S-methyl-thiosemicarbazone chelates. Characterisation of the compounds in the [Fe(L)CI] and [Ni(L)] general formula was accomplished by means of elemental analysis, conductivity and magnetic measurements, H-1 NMR, UV-vis, IR and mass spectroscopy. Cytotoxicity and proliferation experiments using K562 chronic myeloid leukemia cell line and ECV 304 human endothelial cell line imply that the iron(111) chelates may have antileukemic effects with 3.5 mu g/dl LD50 dose. (c) 2006 Elsevier Masson SAS. All rights reserved.