We searched for evidence of aberrant movement or position of segregant set chromosomes in C-banded and G-11-banded early-phase hamster-mouse and hamster-human cell hybrids that had been prepared with minimal disruption. No evidence was obtained for an increased frequency of multipolar mitosis, delayed or precocious metaphase congression or anaphase segregation, or for exclusion of chromosomes from the daughter nuclei. However, in hamster-human hybrids, segregant set (human) chromosomes were observed to assume a central position within a ring of hamster chromosomes on the metaphase plate. Such non-random positioning may imply that the centromeres of segregant chromosomes make aberrant, or simply less efficient, attachments to the spindle in hybrid cells. This aberrant position may perhaps result indirectly in chromosome loss by interfering with the normal processes of replication, repair or transcription.