The homeologous Orp1 and Orp2 regions of maize and the orthologous regions in sorghum andrice were compared by generating sequence data for 486 kb of genomic DNA. At least three genicrearrangements differentiate the maize Orp1 and Orp2 segments, including an insertion of a single geneand two deletions that removed one gene each, while no genic rearrangements were detected in the maizeOrp2 region relative to sorghum. Extended comparison of the orthologous Orp regions of sorghum andjaponica rice uncovered numerous genic rearrangements and the presence of a transposon-rich region inrice. Only 11 of 27 genes (40%) are arranged in the same order and orientation between sorghum andrice. Of the 8 genes that are uniquely present in the sorghum region, 4 were found to have single-copyhomologs in both rice and Arabidopsis, but none of these genes are located near each other, indicatingfrequent gene movement. Further comparison of the Orp segments from two rice subspecies, japonica andindica, revealed that the transposon-rich region is both an ancient and current hotspot for retrotransposonaccumulation and genic rearrangement. We also identify unequal gene conversion as a mechanism formaize retrotransposon rearrangement.