We examined the degree of conservation of gene order in two plant species, Prunus persica (peach) and Arabidopsis thaliana (thale cress), whose lineages diverged more than 90 million years ago. In the three peach genomic regions studied, segments with a gene order congruent with A. thaliana were short (two to three genes in length); and for any peach region, corresponding segments were found in diverse locations in the A. thaliana genome. At the gene level and lower, the A. thaliana sequence was enormously useful for identifying likely coding regions in peach sequences and in determining their intron-exon structure. The peach BAC sequence data reported here contained a BLAST-detectable putative coding sequence an average of every 7 kb, and the peach introns identified in this study were, on average, almost twice the length of the corresponding introns in A. thaliana.