Because of excellent and readily available animal models of infection with Strongyloides species, much of the basic biology of the parasite was understood by the early 1930s. Only selected issues of major physiologic importance were left to be addressed by intentional human infections. Concern about the strongyloides hyperinfection syndrome and the parasite's characteristic refractoriness to drug therapy led investigators of experimental human infections to act as subjects. This article reviews studies that describe experimental human infection with Strongyloides stercoralis and Strongyloides fülleborni as well as other Strongyloides species. These studies address two main issues: the clinical manifestations associated with the prepatent and early patent phases of infection, and the development of immunity to reinfection in individuals previously infected. The possible conclusions from these studies are discussed in the context of the current understanding of natural human and experimental animal infections.