We present Expression Comparison, a tool to compare expression patterns between species. It uses curated annotations of homology between anatomical structures, such as organs or tissues. Expression calls are based on the curated transcriptome data integrated within the Bgee database. Gene homology can be of any type, from user input. The results are presented according to conservation of pattern, as well as rank of expression per species. Expression Comparison is freely available on the Bgee website: https://bgee.org.