To determine differential gene expression profiles in the venom gland and sac of Orancistrocerus drewseni Saussure (1857), we generated a subtractive cDNA library using PCR-selective cDNA subtraction system. After cDNA cloning and sequencing of 536 clones, 498 expressed sequence tags (ESTs) were clustered and assembled into 94 contigs and 111 singletons. About 65% (134) of 205 contigs and singletons had the matched BLASTx hits (E £ 10^-4). Most of the sequences (108 sequences, 80%) with matched BLASTx hits were homologous to the genes from Hymenoptera, particularly Apis mellifera (103 sequences). Of 134 sequences, 115 sequences were similar to proteins with assigned molecular function in the Gene Ontology database, while 19 sequences were matched to proteins that the molecular functions have not been established. The most common functional categories were ²motor activity″, ²catalytic activity″, and ²binding″. The motor activity and binding category contained muscle and cytoskeleton proteins likely derived from the venom sac. The catalytic activity category contained various enzymes including hyaluronidase, phospholipase A2, and ones involved in synthesis of bioactive peptides. Discovery of venom gland-specific genes in O. drewseni should promote further studies on bioactive ingredients in the venom of solitary hunting wasps.