During viral infection, viral immediate-early (IE) genes encode regulatory proteins critical for the viral life cycle. Here we screened white spot syndrome virus (WSSV) IE genes with cycloheximide (CHX)-treated primary culture of crayfish hemocyte and a WSSV genome tiling microarray. Sixteen ORFs, including a known WSSV IE gene (ie1/wsv069), were identified and confirmed by RT-PCR and time course studies. The 16 identified IE proteins contain four proteins (wsv051, wsv069, wsv100, wsv079) with transcription activity, one (wsv083) with Ser/Thr kinase domain and one (wsv249) previously described to function as an ubiquitin E3 ligase. Furthermore, most of the identified WSSV IE genes cluster in a 14 kb genomic region (WSSV China isolate: 36,052 to 50,300 bp). This type of arrangement may facilitate the coordinate control and rapid expression of IE genes.