Fourteen patients (9 females, 5 males; age range: 22-80 years) with 16 univesiculated hydatid cysts of the liver (O ranging 4.2-14 cm) underwent two sessions of puncture-aspiration-alcohol injection (D-PAI) under real-time US guidance at 3-day intervals. Two patients had postoperative recurrences. One patient was pregnant (9 weeks' gestation): her cyst doubled its volume over 2 months. One patient had HBV chronic hepatitis treated by means of interferon: also in this case the cyst doubled its volume. The remaining were high-risk patients for surgery or had refused operation. At US follow-up (ranging 4-24 months) 6 cysts exhibited complete reconstitution of liver parenchyma. In the extant patients two different US patterns were observed: 1) liquid areas with detached inner membranes (4 cysts); 2) solid inhomogeneous areas (6 cysts). In these cases the volume was reduced by 50-80%. No allergic complication occurred either during or after the procedure. Two patients only were affected with vomiting and fever, which resolved in a few hours. Our results indicate D-PAI of univesiculated hydatid cysts of the liver to be an effective alternative to surgery.