An attempt was made to culture the Cryptosporidia, which had been isolated from the excreta of 24 HIV-infected patients and prepassaged on SCID mice, in an artificial host cell-free medium. The authors examined their impact of rabbit hepatic and renal tissue extracts, hemolyzed rabbit blood, bovine bile, ATP, calves' embryonic serum, bovine serum albumin, glucose, phytohemagglutinine, and concanavalin A, cultivation temperature, and medium pH on growth culture. A total of 72 cultures were tested. Transformation of sporosoites to other types of cells in the culture medium was studied from the first hours to two follow-up months. Completion of the parasite's full life cycle could be observed; all the cultures became weak and degraded in the long run.