Abstract: Three cases of uncomplicated Plasmodium falciparum malaria in Sokoto, Nigeria, between June and July 2006, apparently failed treatment with artesunate monotherapy. Two of the cases fulfilled the World Health Organization’s criteria for low grade resistance level while one case fulfilled the criteria for high grade resistance. Use of artesunate monotherapy and improper use among the population may likely quicken the pace of the emerging resistance to the drug amongst the local strains of the parasites.