Adult Dirofilaria immitis were found in the hearts of 43 of 115 coyotes (Canis latrans) trapped within a 50 km radius of the El Dorado County seat. Of mature coyotes, 45% were positive, with worm numbers averaging 9.0 in females and 16.2 in males. D. immitis microfilariae occurred in the peripheral blood and in lung smears. Microfilariae of Dipetalonema reconditum were present in 14 of the coyotes examined (12%). Several coyotes showed enlarged hearts with gross pathological changes.