The general characteristics of 56 childhood cases of cystic hydatid disease were analysed and the results of mebendazole therapy versus surgery were verified. Pulmonary radiograms and ultrasonography were used in the diagnosis. The cysts were localized primarily to the lungs. Twenty seven patients were surgically-treated, with eight having recurrence after a mean period of 3.6 yrs. Thirty patients received regular mebendazole treatment, in a dose of 50 mg.kg-1 with a mean duration of treatment of 11.7 months. Twenty one patients were cured and discontinued the therapy. Nine still use the drug, seven of whom have had dramatic improvement, while the other two have minimal radiographic changes but subjective improvement in general condition. The lung cysts vanished leaving minimal scars, whilst the liver cysts turned into inactive forms. The surgically-treated and drug-treated groups were similar in age, duration and severity of the disease. The recurrence rate of drug-treated children (1 out of 20) was lower than that of the surgically-treated children (8 out of 27); however, this was not statistically significant.