We describe the cytogenetic findings in two benign thyroid hyperplasias with aberrations of chromosome 19. In the first patient, two of four nodules showed identical translocations involving chromosome 19 and 22: 46,XX,der(19)t(19;?)(q13;?),der(22)t(22;?)(q12;?), the remaining nodules had an apparently normal karyotype. Two nodules from a second patient were karyotyped. One showed a karyotype 46,XX,t(1;19)(p35-36.1;q13) and the other had a normal karyotype. From these results as well as those reported previously, we can conclude that structural changes of chromosome 19 characterize a subgroup of thyroid adenomas, thyroid hyperplasias, or both.