Female Anopheles quadrimaculatus adults were blood fed on 15 mixed breed dogs 4 h after the dogs were given oral dosages of ivermectin. Dogs were divided into 5 treatment groups of 3 dogs each, at 10, 500, 1,000, 2,500 micrograms/kg, and untreated. Additionally, An. quadrimaculatus were fed on lambskin-membranes containing blood drawn from one dog in each treatment group. Mosquitoes were allowed to feed on the dogs or the lambskin-membranes and were observed for death at 24 and 48 h post-feeding. Greater than 90% mortality was recorded in all ivermectin treatment groups except at the 24 h post-feeding period with the 10 micrograms/kg dog dose blood fed through the lambskin-membrane (65.4% mortality). The highest 2 dosages produced 100% mosquito mortality at 48 h post-feeding from either a dog or the in vitro system using a lambskin-membrane.