The aims of this study were to investigate the efficacy of a new percutaneous treatment of hydatid cysts of the spleen and to present the results of long-term follow-up. Nine patients (six men, three women; median age 37 years) with 10 hydatid cysts in the spleen underwent a new percutaneous treatment. The procedure included the puncture and free drainage of the cyst fluid under sonographic guidance. After drainage has stopped, alcohol 96% and polidocanol 1% were used as sclerosing agents. The patients were followed up with periodic sonographic examinations. The median follow-up period was 39 months (range: 6-64 months). The median diameter of the cysts decreased from 63.0 mm to 33.3 mm (P < 0.01). The entire cyst cavity filled with a solid echo pattern in three cysts, two thirds of the cyst cavity showed a pseudotumor pattern in three cysts, and one third of the cyst cavity showed a pseudotumor pattern in four cysts. Apart from an urticarial reaction, no major complications occurred during the follow-up period. One patient had under-gone splenectomy due to persistent left upper quadrant pain eight months after treatment. Long-term results indicate that this new treatment modality of splenic hydatidosis is an effective and safe method and causes no major complications.