Anticoccidial drugs are widely used for the control of coccidiosis in the fowl which has inevitably led to the development of drug resistance. Resistance has developed to all of the compounds that have been introduced and if chemotherapy is to remain the principal method of control of coccidiosis, it will be important to continue the search for new anticoccidial agents. Knowledge of biochemical pathways present in the Eimeria parasite and how they differ from those of the host might help identify novel targets for inhibition. Studies of the mode of action of drugs are required if the biochemical mechanisms of resistance are to be understood. Information on the genetic origins of resistance, the stability of resistance and the factors involved in the spread of resistance throughout parasite populations is required. Since there are no methods at present to prevent resistance, more attention should be given to developing strategies for preserving the efficacy of anticoccidial drugs.