This paper summarizes the efficacy and safety evaluation of ivermectin given as a single subcutaneous injection for the control of a wide range of nematode and arthropod parasites of cattle. lvermectin for the treatment and control of parasites in cattle was evaluated in 56 efficacy studies and 181 field trials prior to market introduction. A total of 8,205 cattle were involved, of which 5,094 received ivermectin at 200 mcg/ kg or more, the remainder serving as contemporary controls. It is concluded from the data that ivermectin is safe forcattle when used under practical husbandry conditions at the recommended use level. Subsequent to the compiling of the data for registration submission and prior to large scale commercial use of ivermectin injection, a total of 20,838 cattle in 18 countries were successfully involved in the research and developmenteffort.