A 5BS/5RmS translocation chromosome spontaneously recovered from a ‘Chinese Spring’ — Secale montanum wheat-rye telocentric 5RmS addition line has been identified and cytologically studied using C-banding in somatic and meiotic cells. Analysis of the translocated chromosome showed that a terminal segment of the short arm of 5B had been replaced by a short terminal region of chromosome arm 5RmS. The translocation led to the deletion of the genetic system promoting pairing located in 5BS, which is slightly compensated for when doses of 5RmS are increased, indicating homoeology to wheat chromosome 5BS. The α-amylase phenotype in 5B/5Rm translocated material was studied and found to be identical to that of ditelocentric line 5BL of ‘Chinese Spring’. An effect on the α-amylase activity was detected as a result of the removal of the terminal region of 5BS, perhaps as a consequence of variation in dormancy period duration.