A survey of canine heartworm(Dirofilaria immitis) infections among dogs in Daefu area was performed from February 2000 to October 2002 using a microfilarial test and an antigen test(AGEN$^{TM}$ Canine heartworm). The infection rate of 220 dogs(96 males, 124 females) was 23.2%(51/22) by the microfilarial test, but was 23.6%(52/220) by the antigen test, revealing that 1 of 52 antigen-positive dogs were microfilaria-negative in the peripheral blood. All dogs that were microgilaria-positive were also antigen-positive. The infection rates of heartworm in dogs at the age of < 1, 1-3, 4-6, 7-11 and 12-15 years were 2.7%, 17.4%, 41.0%, 42.9% and 57.1%, respectively. Based on the fact that the antigen test is more accurate than the microfilaria test. The infection rates of heartworm in dogs by housing of indoor and outdoor were 6.9% and 46.4%, respectively. Based on the fact that outdoor housing is more infectious than indoor housing.