Visceral leishmaniasis (VL), caused by the protozoan Leishmania sp., affects 500000 people annually, with the Indian subcontinent contributing a significant proportion of these cases. Emerging refractoriness to conventional antimony therapy has emphasised the need for safer yet effective antileishmanial drugs. Artemisinin, a widely used antimalarial, demonstrated anti-promastigote activity and the 50% inhibitory concentration (IC(50)) ranged from 100 microM to 120 microM irrespective of Leishmania species studied. Leishmania donovani-infected macrophages demonstrated decreased production of nitrite as well as mRNA expression of inducible nitric oxide synthase, which was normalised by artemisinin, indicating that it exerted both a direct parasiticidal activity as well as inducing a host protective response. Furthermore, in a BALB/c model of VL, orally administered artemisinin (10mg/kg and 25mg/kg body weight) effectively reduced both splenic weight and parasite burden, which was accompanied by a restoration of Th1 cytokines (interferon-gamma and interleukin-2). Taken together, these findings have delineated the therapeutic potential of artemisinin in experimental VL.