A series of bis-indolone-N-oxides, 1a-f, was prepared from bis(ethynyl)benzenes and o-halonitroaryls and studied for their in vitro antiplasmodial activities against Plasmodium falciparum and representative strains of bacteria and candida as well as for their cytotoxicity against a human tumor cell line (MCF7). They did not cause any haemolysis (300 μgmL(-1)). Of the synthesized bis-indolones, compound 1a had the most potent antiplasmodial activity (IC50=0.763 μmolL(-1) on the FcB1 strain) with a selectivity index (CC50 MCF7/IC50 FcB1) of 35.6. No potency against the tested microbial strains was observed.