The molecular characterization of C-banded regions of Secale montanum Guss. by means of in situ hybridization was performed in order to provide new information about their chromosome structure relative to cultivated rye, Secale cereale L. Accurate identification of individual chromosomes was achieved using simultaneous and (or) successive fluorescent in situ hybridization (FISH) and C-banding. FISH identification was performed using total rye DNA, three highly repetitive rye DNA sequences (pSc119.2, pSc74, and pSc34), and the ribosomal RNA probes pTa71 (18S, 5.8S, and 26S rDNA) and pTa794 (5S rDNA). FISH was also used to identify the chromosome segment involved in two spontaneous translocation lines recovered from a 'Chinese Spring'--S. montanum wheat-rye addition line. FISH analysis revealed the exact translocation breakpoints and allowed the identification of the transferred rye segments. The value of this type of analysis is discussed.