Female Culicoides variipennis were fed at 1-18 days postinoculation on calves treated with a commercial injectable formulation of ivermectin at the recommended rate of 200 micrograms/kg of body weight. There were no significant differences between treated and untreated animals in the survival rate of the flies at 24 h and 48 h postinoculation and the number of eggs produced per living female. There was a significantly greater mean hatch rate of eggs from flies fed on the untreated animals (65.8%) than those fed on the treated animals (52.8%). The recommended use rate of ivermectin does not appear to provide significant mortality for female C. variipennis, nor affect egg deposition or hatch rate sufficiently to reduce vector populations.