There were no significant differences in body weight gains, FAMACHA? and body condition scores amongst the three treatment regimens for ewes that did not conceive. For those that became pregnant during the trial there was a significant difference when analysed by calendar date but not when analysed by reproductive stage. There were also no significant differences between trial groups in lamb birth weight and, after slow growers had been sold, the average daily gain of the lambs born to ewes in the trial. The cost of anthelmintics was considerably lower for the FAMACHA? group. In conclusion there were no significant differences in selected production parameters when using the FAMACHA? system as opposed to other methods of anthelmintic use in a Mutton Merino flock in a semi-intensive farming system and that the gestation status should be taken into account when measuring these parameters in future studies.