Cytogenetic investigation was performed on direct preparations of 15 endometrial cancers showing different histotypes. Clonal abnormalities were found in 11 out of 13 analysable cases. The modal chromosome number was near diploid in all cases. The abnormal karyotypes contained relatively simple numerical or structural aberrations in the majority of tumours. In contrast, two neoplasms with serous papillary and mixed mullerian morphological features shared multiple complex changes as well as cytogenetic evidence of intratumoral heterogeneity. The most frequent chromosome abnormality in our series of endometrial neoplasms was 6q deletion, which was detected in serous papillary, endometrioid and mixed mullerian tumours. The loss of the 6q region, which is also frequently involved in ovarian carcinoma, suggests a relationship between endometrial and ovarian cancers based on a common histogenesis.