Specimens of Dirofilaria sp. removed from eight Italian patients were identified as D. repens by morphology and confirmed as such by a PCR-based method of DNA analysis. Blood samples were also drawn from the patients so that two serological tests (ELISA and western blot), one based on the recognition of molecular markers recently identified in the somatic antigenic complex of D. repens, could be evaluated. The antigenic complex used in the ELISA only gave a weak sensitivity. However, the western-blot assays, based on the polypeptide molecular markers, were found to have greater sensitivity and should be useful in detecting human cases of dirofilariasis.