The relationship between sonographic image and histological findings of 149 hepatic hydatid cysts was studied in 98 patients with primary hepatic hydatid disease. Sonographic classification was based on the morphology and structure of the cyst, which is thought to correspond to developmental stages of the hydatid cyst. The types were classified as follow: Type I: simple fluid-filled cyst denoted as the early stage of the disease; Type II: with undulated membrane representing detached endocyst secondary to rupture; Type III: with daughter cysts and a formed echogenic material called matrix; Type IV: solid cyst filled with matrix; Type V: calcified cyst. The latter two types were dead cysts, denoting the end of natural fate of the cyst. The natural progression of the cyst from Type I to Type V was correlated with increasing age of the patients. The rate of stainable protoscolices corresponded to the degree of damage of the germinal membrane, which could reflect the viability of hydatid cyst. The damage of germinal membrane happened earlier and was more severe than that of the protoscolices, being the biologic basis of transforming from type II into type III. Our study also showed that normal, damaged and dead cysts accounted for about 1/3 respectively in the clinical cases of hepatic hydatid disease, providing references for evaluating chemotherapeutic effects on hepatic hydatidosis.