We describe here four cases of disseminated strongyloidiasis. In Okinawa, it has been reported that about 10% of the residents are infected with Strongyloides stercoralis, but disseminated cases are rare. Detailed histopathological examination revealed that the present four cases could clearly be separated into two groups, two acute cases and two subacute cases. The acute cases died rapidly due to extensive diffuse intra-alveolar haemorrhage in both lungs. However, there were no inflammatory infiltrates, abscesses or granulomas in the lungs. Worms were demonstrated in the alveolar spaces. No extensive bleeding was observed in any organs except the lungs. The acute cases could be diagnosed as severe diffuse intra-alveolar haemorrhage syndrome, but deposition of immune complex (parasite antigen and immunoglobulins) and complement C3c was not demonstrated in the alveolar wall and small vessels of the lung. The subacute cases exhibited no such extensive haemorrhage, but scattered microabscesses were found with sepsis. During the migration of the worms from the colon, enteric bacteria entered the circulation in the two subacute cases. The acute cases received steroid therapy before the dissemination of the worms, but the two subacute cases did not. Steroids might have influenced the Strongyloides stercoralis dissemination and/or the course of the disease. (C) 1998 Australian Society for Parasitology. Published by Elsevier Science Ltd.