The cytogenetic findings in a group of 15 polycythemic patients are reported. G and C banding techniques were used on bone marrow and peripheral blood preparations. Major chromosomal aberrations were found in four out of the 15 patients, an incidence similar to that found in other studies on polycythemia. The most interesting finding concerned the chromosomal polymorphism of the pair 19. A possible relation to the etiology of the disease is discussed.