Efficacy of chlorpyriphos (Classic*20, 20% EC) and deltamethrin (Butox, 1.25% EC) was assessed by spraying these drugs on cattle and buffaloes which were naturally infested with ticks at the concentration of 2.5 and 2 ml/l, respectively. Results of the study demonstrated the prolonged effect of chlorpyriphos when compared with deltamethrin. Moreover, residual effect of chlorpyriphos remained even after 14 days of treatment with 28.57% animals showing reinfestation, while in deltamethrin treated animals; the tick number started increasing after 14th day of treatment with 50% animals showing reinfestation on 14th day post-treatment.