Quinine remains a reliable treatment for falciparum malaria in most parts of the world. We report recrudescence of imported Plasmodium falciparum malaria following quinine treatment in the context of concurrent phenytoin use. Supported by a subtherapeutic quinine level, we hypothesise that a drug interaction with phenytoin may compromise the efficacy of quinine in the treatment of malaria. (c) 2005 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved.