Porcine genomic DNA encoding a 55 kDa subunit of interleukin-2 receptor (IL-2R), which is termed alpha chain (IL-2Ralpha), was cloned by repeated plaque hybridization using IL-2Ralpha cDNA as a probe. Two different lambda phage clones, one of which encoded exon 1 and the 5'-upstream flanking region of IL-2Ralpha gene and another encoded the sequence from exon 2 to exon 8, were isolated. By analysis of the 5'-upstream region of the gene, putative binding motifs for transcription factors such as GATA family proteins, Ikaros, NF-kappaB, NF-IL2Ralpha and SRF, were found as described in human, murine and bovine genes. Two additional motifs for STAT4 binding were also found in this region. Moreover, using the FISH technique, we assigned the porcine IL-2Ralpha locus to the distal end of the long arm of chromosome 10 (10q6-qter) where the vimentin gene had been assigned nearby.