Differences in the level of chromosome pairing in hybrids between 'Chinese Spring' wheat homoeologous group 3 aneuploids and rye and in homoeologous group 3 aneuhaploids were studied. Factors affecting chromosome pairing were detected or confirmed on both arms of the chromosomes of homoeologous group 3 in wheat. Effects were also identified on chromosome 3R of rye and a chromosome of Hordeum bulbosum. Factors affecting crossability between 'Chinese Spring' wheat and H. bulbosum were also found on chromosomes 3A, 3B, and 3D. A correlation was shown between increased pairing and reduced crossability.