We report the clinical and laboratory findings in three unrelated families from southeastern Brazil with Sp alpha I/65 hereditary elliptocytosis (HE), including one homozygote and a patient presenting an elongated beta-spectrin. In family 1, three patients presented the allele alpha-Lely in trans to the elliptocytogenic allele. In these three patients the blood smear showed pronounced elliptocytosis, poikilocytosis and a few small red cell fragments instead of the mild elliptocytosis observed in their father, who did not present the polymorphism. In family 2 we describe one homozygote, with consanguineous parents presenting with anaemia, splenomegaly, severe poikilocytosis and elliptocytosis, budding, microspherocytes and numerous fragments in the blood smear. In family 3 we found an elongated beta Sp in a patient with Sp alpha I/65. The cause of the HE was the Sp alpha I/65 since the elongated beta Sp was not found in his brother, who also presented with HE and Sp alpha I/65. Apparently the abnormal beta Sp did not aggravate the HE, because both individuals had the same clinical and laboratory findings. However, the propositus presented a few more elliptocytes and poikilocytes than his brother, probably because the elongated beta-spectrin may have disturbed the spectrin self-association. In fact, in the propositus an abnormal band was observed in the nondenaturing gels, just above the Sp dimer, probably as a result of the association of the abnormal beta Sp with the normal spectrin chains. In the family studied here, both brothers presented the allele alpha Lely, but as their mother was dead, it was not possible to determine the polymorphism transmission. However, the high number of poikilocytes observed in the blood smear of both cases suggests an association in trans with the Sp alpha I/65. Thus, taken together, the data in this report indicate that HE secondary to Sp alpha I/65 abnormality is frequent in Brazil, and in one case it was associated with an apparently novel abnormal large beta-spectrin.94470-5