Abstract A study was carried out to determine and compare the pharmacokinetics of isometamidium in groups of six animals each of sheep and goats treated by intramuscular injection with isometamidium chloride (Samorin ® , Rhone Merieux, Lyon, France) at 0.5 mg/kg body weight. The animals were bled at pre-determined time intervals and serum isometamidium concentrations monitored using isometamidium-ELISA for a period of over 60 days post-treatment. Pharmacokinetic evaluation was carried out using a non-compartment analysis. Mean residence time (MRT) in sheep was higher but not significantly different from that observed in goats. Whereas the mean C max values observed in both species were similar, the T max value of 12.7 h obtained in goats was significantly longer ( P P