Four trials, using 48 European breed cattle, were conducted to evaluate the efficacy of abamectin against the louse species Linognathus vituli, Haematopinus eurysternus and Damalinia bovis and against the mange mites Sarcoptes scabiei var bovis and Psoroptes ovis. Animals were allocated by restricted randomisation based on parasite counts to treatment with abamectin at a dose of 200 micrograms/kg given subcutaneously or to an untreated control group. Ectoparasites were counted before treatment and at weekly intervals thereafter for eight weeks. L. vituli, H eurysternus and S scabiei var bovis were eliminated (P < 0.05) by day 7 after abamectin treatment. An efficacy of more than 99 per cent was recorded against P ovis mange mites. The biting louse D bovis was not controlled. Abamectin treatment increased the weight gain of cattle infested with ectoparasites.