Cytogenetic studies using constitutive heterochromatin variations represent one of the best method in documentation of allogeneic bone marrow transplantation (BMT). Sex mismatched transplants are evaluated by gonosomal examination. In sex matched patients, several banding techniques are performed before BMT to detect autosomal polymorphism in donor and recipient. Can be informative: chromosomes 3 and 4 centromere, acrocentric centromere and satellites, chromosomes 1, 9 and 16 secondary heterochromatic constriction. Authors describe their methodology for these studies and results about 81 patients.