Five hundred and twenty‐one dogs, at least one year of age, visiting a private veterinary clinic in Paramaribo, were examined from August 1977 till August 1978. Twenty‐six per cent had microfilariae of Dirofilaria immitis in their peripheral blood. The mean number per infected dog was 9,689 per ml of blood (range 14 to 78,984 per ml). Microfilaria positivity rates were significantly greater in older dogs, and there were significantly more abnormal SGPT values in positive than in negative dogs, but there were no significant associations between positivity rate and alcalic phosphatase, ureum, or creatinin values, presence of clinical symptoms, presence of antibodies to Dirofilaria immitis (measured by the direct Immuno Fluorescent Antibody test), sex, breed nor neighbourhood of residence of the dogs.