This study provides a contribution to understanding of the natural history of the hydatid cyst during its evolution in the human liver examining the high morphostructural variability of larval forms of Echinococcus granulosus. A detailed study of a large sample of intact cysts removed from patients surgically treated by means of total pericystectomy, has enabled to outline the different developmental stages of the parasite over time, up to its death and complete degeneration.