The effect of subcutaneously injected diclazuril on the output of Eimeria species oocysts was studied in experimentally infected rabbits. Diclazuril was administered either prophylactically at 0·5, 1 or 2 mg/kg bodyweight two days before each rabbit was inoculated with 20,000 oocysts of a mixed-species field isolate of Eimeria or therapeutically at 1, 2 or 4 mg/kg bodyweight five days after they were inoculated. The prophylactic treatments significantly reduced (P<0·05) the output of oocysts in faeces and the numbers in the rabbits' livers at all doses. The therapeutic treatment at 4 mg/kg also caused a significant reduction (P<0·05) in oocyst shedding, but the lower doses resulted in only a moderate reduction. The shedding of the pathogenic species Eimeria stiedae, Eimeria magna, Eimeria irresidua, Eimeria flavescens, Eimeria piriformis and Eimeria intestinalis was significantly reduced (P<0·05) in all the treated groups. The burden of oocysts in the livers of the therapeutic groups (4000 to 9000) were significantly lower (P<0·05) than in the inoculated but untreated control group (23,000), but higher than in the prophylactic groups (around 1000).