Hydatidosis is a zoonosis caused by Echinococcus in the larval stage. Humans are accidental intermediary hosts where cystic lesions develop, primarily in the liver and the lungs. It is usually asymptomatic, hence it often represents an incidental finding. Symptoms result from cyst expansion and/or host inflammatory reaction. Hepatomegaly is the most common sign. Hydatidosis induces no specific changes in lab tests but immunodiagnostics are available that may complement its study, with antibody detection being the modality of choice. While ultrasound is the main diagnostic technique, tomography offers more accurate information regarding both characteristics and anatomical relations. A number of therapy options are presently available. Treatment with albendazole, whether combined or not with praziquantel, is useful for smaller, uncomplicated cysts (< 5 cm). Only 30 % of cysts disappear with medical treatment alone. Surgery is indicated for bigger liver cysts (> 10 cm), and cysts at risk of rupture and/or complicated cysts. The laparoscopic approach is scarcely widespread. The radical technique (total cystopericystectomy) is preferable because of its lower risk for postoperative abdominal infection, biliary fistula, and overall morbidity. Conservative techniques are appropriate in endemic areas where surgery is performed by nonspecialist surgeons. PAIR (puncture-aspiration-injection-reaspiration) is an innovative technique representing an alternative to surgery. It is indicated for inoperable cases and/or patients who reject surgery, for recurrence after surgery, and for lack of response to medical treatment. Active surveillance without treatment may be indicated for quiescent or inactive, uncomplicated liver cysts.