The paper reports available data on 72 known human cases of polycystic echinococcosis (PE) caused by Echinococcus vogeli (Ev) or E. oligarthrus (Eo). The patients' ages ranged from 6 to 78 years (median 44); one third were younger than 22 years and had severe lesions, demonstrating the aggressiveness of PE. There were no differences in occurrence between sexes. In 80% of the cases the lesions were in the liver alone or in combination with other organs; the rest were located in the lung or other single sites. The diagnosis of PE was based on the demonstration of polycystic larval cestode lesions by radiological imaging (X-ray, US, CT scan) in patients born in tropical sylvatic areas of America where wild carnivores (canids, felids) and rodents (pacas and other species) were present. Serologic tests often, but not always, supported the diagnosis. Species identification of Ev or Eo were based on morphological characteristics of rostellar hooks from protoscoleces. The most common clinical presentation was abdominal; hard, round masses in or connected with the liver, hepatomegaly, increased abdominal size, pain, marked weight-loss and fever. Signs of portal hypertension were also present in 25% of cases, all of whom died of the disease or surgical complications following biliary drainage or partial hepatectomy. Ten percent were in asymptomatic persons. Albendazole treatment resulted in clinical improvement and disappearance or reduction of the size of lesions in some patients observed up to 24 months. The author believes that albendazole treatment should be tried before any other treatment is implemented. Human PE was reported from 11 countries, from Nicaragua to Argentina, 31 case were due to E. vogeli, three to E. oligarthrus (two orbital from Venezuela and Surinam and one cardiac from Brazil) and 38 were due to Echinococcus sp. (no rostellar hooks were available). PE reported from Nicaragua, Costa Rica, Chile, Argentina and Uruguay, countries outside the geographical range of the bush dog (only natural host of Ev) may have been due to Eo rather than to Ev. Several felids are known to serve as final host of Eo, and they are present in those areas. Epidemiological field studies of autochthonous human populations in tropical areas may contribute to early detection and make possible greater success in treatment of polycystic echinococcosis.