The GeneChip Drosophila Genome 2.0 Array provides comprehensive coverage of the Drosophila melanogaster genome and is an important tool for developmental biology. The array can be used to study expression of over 18,500 Drosophila melanogaster transcripts and was developed based on the content from the recent annotation (release 3.1) of the Drosophila melanogaster genome by FlyBase and the Berkeley Drosophila Genome Project (BDGP),funded by the National Human Genome Research Institute, Department of Energy, and the Howard Hughes Medical Institute In addition, other published gene predictions from the Drosophila research community were included on the array, which includes over 30% more content than the previous-generation Drosophila melanogaster design.