East Coast fever, caused by the protozoan parasite Theileria parva, kills about 600,000 cattle annually in Africa. The hydroxynaphthoquinone compound buparvaquone (BPQ) is curative. Sixteen calves were infected with T. parva. On manifestation of disease symptoms, eight were injected with the original (pioneer) BPQ product and eight with a test product containing BPQ. All 16 calves were cured by one injection of 2.5 mg BPQ/kg bodyweight. The concentration of BPQ in blood plasma was monitored by HPLC. The mean observed Cmax of BPQ was 0.229 and 0.253 μg/mL of plasma, the mean observed time to reach this concentration (Tmax) was 2.62 and 2.12 h and the AUC (area under curve) was 4.785 and 4.156 μg h/mL, respectively, for the pioneer and test product. Considerable variations occurred in the plasma concentration of BPQ within each group. They showed no relationship with either clinical or parasitological parameters following treatment.