The interleukin-12 receptor (IL-12R) is composed of two subunits, referred to as beta1 and beta2. Both chains are necessary for high-affinity IL-12 binding and signalling, although only the IL-12Rbeta2 chain contains the intracellular tyrosine residues responsible for STAT4 activation. This study presents the intron-exon organization of the human IL-12Rbeta2-chain gene. Polymerase chain reaction (PCR) primers designed across the cDNA (U46198) were used to trace introns, by comparing PCR product sizes obtained using cDNA and genomic DNA as templates. PCR products spanning introns were sequenced to determine the exact splice sites and flanking regions. The coding region of the gene was found to consist of 15 exons and 14 introns. All intron-exon boundaries are consistent with the consensus sequence for splice junctions (5' GT/AG 3'). Comparison of the intron-exon organization with the human GCSFR gene indicated a remarkably well conserved genomic organization between these two class I cytokine receptors. Interestingly, we identified an alternatively spliced mRNA, encoding a putative, truncated protein, lacking all signalling potential.