Sixty-eight cystic echinococcosis patients were each treated with 800 mg albendazole/day in four 28-day courses separated by 14-day drug-free intervals. Follow-up for 3-7 years showed that this treatment alone eradicated the cysts in many patients; in most of the remainder, disease progression stopped. Of the 59 patients with liver cyst(s), 41% were cured (all cysts disappeared), 17% showed marked improvement (> 25% contraction, complete consolidation), 24% limited improvement and 15% no change. Of the 12 patients with lung cyst(s), 72% were cured, 9% showed limited improvement and 18% showed no change (18%). No patient worsened but a recurrence occurred in two patients at about 56 months. The times taken to detect an initial cyst change and to detect cure were longer than is generally expected; initial cyst changes and cure could only be detected after 1 year in 12% and 69% of patients with liver cysts and 22% and 37% of those with lung cysts, respectively.