The reactivity in solution of two recently characterized gold(III) complexes, AuCl3 (Hpm) and AuCl2(pm), has been investigated in view of their potential use as anti-cancer agents. In water, both compounds undergo relatively fast hydrolysis of the bound chlorides without loss of the heterocycle ligand; the process is much faster within a physiological buffer. When the two gold(III) complexes react with proteins like albumin or transferrin, reduction of gold(III) to gol(I) and or hydrolysis is observed. On the other hand, both complexes bind rapidly and tightly polynucleotides of calf thymus DNA, with gold remaining in the +3 oxidation state. Circular dichroism investigations reveal a large perturbation of DNA conformation upon gold (III) binding; preferential binding to GC sequence is shown. Cytotoxicity studies on a number of humor cell lines demonstrate a good activity of these gold(III) complexes compared to cisplatin. However, quick hydrolysis and/or reduction of these compounds under physiological conditions may represent a severe limitation to their use.