Chromosome studies were carried out in long-term (142 and 184 d) human lymphocyte in vitro cultures in order to investigate the cytogenetic status of aging lymphocytes. The female donors were subdivided into three subgroups according to their age: 20-40 year-old (three individuals), 70-90 year-old (five persons), and centenarians (three persons). Besides some aneuploidy and structural abnormalities, telomere fusions were detected in all donor cells, and associations of acrocentric chromosomes were found in six persons in the three age-groups. Clonal trisomy 2 was present in three individuals (two from the 70-90 year-group and one centenarian with a clone +2, +8). While telomeric fusions and acrocentric associations seem to be more related to in vitro aging, trisomy 2 also appears dependent on the age of the cell donors.