RESUMO
Eighty dogs from a locality west of the Conceição Lagoon, in the Santa Catarina Island, Florianópolis Municipality, State of Santa Catarina, Brazil, were examined for dirofilariasis by thick smear and by modified Knott's method. Twelve of them (15%) were positive, five only by Knott's, two only by thick smear and five by both methods. Positive dogs were observed in several parts of the locality, indicating that the parasite is widespread. Prevalence was significantly higher in older animals. Size, sex, hair length, place of sleeping and hour of blood collection did not significantly influence the results. Forty dogs of the Military Police kennel, at São José Municipality, Santa Catarina State, were all negative. Studies on the transmission and control of dirofilariasis in the region should be developed.