Since 1971, at the Laboratory of Parasitology, Faculty of Veterinary Medicine, University of Bologna, 30 cases of human dirofilariasis were observed out of the 101 cases reported in Italy. The causative agent was identified in nearly all the cases as Dirofilaria repens (Nematoda, Filarioidea) a parasite relatively common in the dog in Italy. 23 cases were localized in the subcutaneous tissue, 4 in the submucosa and 3 in the lungs. In the majority of the cases the diagnosis had been misinterpreted, the lesions being first seen as malignant or benign tumours or foreign-body granuloma. The parasite was histologically recognized. In 3 cases the parasite could be extracted intact from the nodule. The authors believe that human dirofilariasis is more frequent than reported by the relevant scientific literature in that many cases are likely to recover spontaneously while others would remain undetected.