Sixty patients with Echinococcus granulosus infection of the liver, lungs, bone and/or soft tissues were treated for several months with oral mebendazole (50-60 mg kg-1 day-1), in divided doses after fat-rich meals, either without surgery (WS), post-surgery (PS) or pre- and post-surgery (PPS). Long-term follow-up, possible for 52 of the patients, showed that WS, PS and PPS patients have so far remained disease-free following treatment for (means +/- standard deviations) 65.5 +/- 37.7, 82.5 +/- 37.0 and 84.1 +/- 28.3 months, respectively. Ultrasound and computed tomography scans were similar in WS and PPS patients post-treatment. Blood eosinophil levels, which were sometimes elevated initially, returned to normal in all patients and this decrease indicated cyst degeneration before this was evident on the scans. Treatment of patients with cystic echinococcosis may no longer require surgery.