- Summary Six cystic echinococcosis patients underwent surgery for the removal of echinococcal cysts. All were treated with albendazole prior to and following treatment. After surgery, no cysts were detected in five of the six patients examined. Both ELISA and immunoblot analysis have been used to determine specific IgG, IgG4 and IgE activities. Total elimination of IgG and IgG4 was not achieved in any of the patients studied. Prior to the first surgery/treatment, specific IgG, IgG4 and IgE antibodies were demonstrated in all patients, except one who did not show any IgE activity. The first treatment was followed by highly elevated IgE in two patients; in one of them it was further combined with an apparent decrease in IgG activity. Repeated treatment with albendazole given 0.8–8.5 years after the first treatment/surgery was followed by either moderate or highly reduced IgE activity in two patients, respectively, and a slight increase in IgG4 in another patient. A third course of treatment, given 2–2.5 years after the second treatment, barely affected the antibody activities. The present study suggests that anti-echinoccocal antibody activity may remain high many years after successful cyst removal. Determination of IgG, IgG4 and IgE responses is preferable for the assessment of treatment results. The presence of anti-echinococcal antibodies after surgery with no cyst detection does not necessarily indicate an active echinococcal infection.