In our study, we arbitrarily define complex hydatid cysts of the liver as either cysts with a diameter > or =10 cm, or as multiple and recurrent cysts. These types of cysts were then divided into two subgroups: giant cyst identified as a cyst with a diameter > or =10 cm, and complicated cyst as multiple, recurrent, abscessed cysts, or those resistant to conservative treatment. The aim of this study was to retrospectively analyze a series of 38 consecutive patients who underwent surgery for complex hydatid cysts over a period of 9 years at the same institute to determine the evolution of the surgical treatment and the risk factors for recurrence. Fourteen (36.8%) of these patients were women and 24 (63.2%) men (median age 48.1; range 16-71 years). The mean postoperative followup was 24 +/- 10.8 months. All patients were treated prophylactically with albendazole (10 mg/Kg/day) for 15 days preoperatively and for 2 months postoperatively. Partial cystectomy was performed in two cases (5.26%) and radical pericystectomy in 20 cases (52.63%). In 15 cases the patients underwent liver resection (39.47%): left hepatectomy was performed in eight cases (21.05%), and right hepatectomy in seven cases (18.42%). In one case, both wedge resection and pericystectomy were performed. There were no deaths and only one patient (2.63%) showed signs of recurrence at follow-up. Radical surgery is the most effective treatment for complex hydatid cysts. In our experience, partial or total pericystectomy virtually eliminated, over time, the need for hepatic resection.