In the 15 years from 1960 through 1974, 58 patients (38 male and 20 female) from 3 to 18 years of age were treated. In 24 only the lungs were involved, in 23 only the liver, and in 2 both organs were involved. Various other organs including the orbit, omentum, kidney, uterus, brain, and spinal cord contained cysts in one or more cases. Diagnosis was by X-ray, angiography, and myelography. The Casoni skin test was positive in 36 of 43 (83.7%) trials. All patients were treated surgically and, except for one death from pneumonia, all did well.