Using fluorescence in situ hybridization (FISH) we localized introduced genes on metaphase chromosomes of barley, wheat, and triticale transformed by microprojectile bombardment of microspores and scutellar tissue with the pDB1 plasmid containing the uid A and bar genes. Thirteen integration sites were detected in the nine lines analysed. Southern analysis showed that three or more copies of the plasmid were present in the lines. In a triticale line containing four copies three different integration sites were identified, indicating that the method described is sensitive enough for the detection of single-copy integrations. There was a slight tendency towards the localization of transgenes in distal chromosome regions. Using the GAA-satellite sequence for chromosome banding, the chromosomes containing the inserted genes were identified in most cases. Two barley lines derived from the same transformant showed a totally different integration pattern. Southern analysis confirmed that the inserted genes were segregating independently, resulting in different integration patterns among the progeny lines. The application of the FISH technique for the analysis of transgenic plants is discussed.