Intronless genes (IGs) fraction varies between 2.7 and 97.7% in eukaryotic 
genomes. Although many databases on exons and introns exist, there was no 
curated database for such genes which allowed their study in a concerted manner. 
Such a database would be useful to identify the functional features and the 
distribution of these genes across the genome. Here, a new database of IGs in 
eukaryotes based on GenBank data was described. This database, called IGD 
(Intronless Gene Database), is a collection of gene sequences that were 
annotated and curated. The current version of IGD contains 687 human intronless 
genes with their protein and CDS sequences. Some features of the entries are 
given in this paper. Data was extracted from GenBank release 183 using a Perl 
script. Data extraction was followed by a manual curation step. Intronless genes 
were then analyzed based on their RefSeq annotation and Gene Ontology functional 
class. IGD represents a useful resource for retrieval and in silico study of 
intronless genes. IGD is available at http://www.bioinfo-cbs.org/igd with 
comprehensive help and FAQ pages that illustrate the main uses of this resource.