Cytogenetic studies on carcinoma of the cervix have shown the nonrandom involvement in structural changes of a number of chromosomes, particularly chromosomes 1, 3, 5, 11, and 17. Apart from chromosome 5, where a short-arm isochromosome is the commonest derivative, these chromosomes most often undergo short-arm deletions. Notably, chromosome 17 may have undergone structural changes that result in loss of the tumor suppressor gene TP53 on 17p; chromosomal translocations may in some tumors perform the function that in others is provided by human papillomavirus protein complexing with and inactivating this gene. The chromosome 1 changes may sometimes result in the duplication of long-arm material. Although there have been few comparable studies on the preinvasive stages of cancer of the cervix, it is clear from earlier chromosome and quantitative DNA studies that, except perhaps in the "mild dysplasias," there already is clonal development that has resulted in an aneuploid population with a mode that, as in carcinomas, is either in the diploid or (in 50% or more) triploid-tetraploid range; spindle defects are prominent and may result in unequal segregation of the chromosomes into the daughter cells. Further characterization of the chromosomal changes in carcinoma of the cervix, and more particularly its preinvasive stages, using the new molecular DNA techniques is eagerly awaited.