The aim of this study was to assess the possible association between the protein tyrosine phosphatase non-receptor 22 (PTPN22) gene 1858C-->T (rs2476601, encoding R620W) polymorphism and inflammatory bowel disease (IBD). Our study population consisted of 1113 IBD [544 ulcerative colitis (UC) and 569 Crohn's disease (CD)] patients and 812 healthy subjects. All the individuals were of Spanish white origin. Genotyping of the PTPN22 gene 1858C-->T polymorphism was performed by real time polymerase chain reaction technology, using TaqMan 5'-allelic discrimination assay. The frequency of the PTPN22 1858T allele in healthy subjects was 6.2% compared with 6.7% in the UC patients and 5.1% in Crohn's patients. No statistically significant differences were observed when the PTPN22 1858C-->T allele and genotype distribution among CD patients, UC patients and healthy controls were compared. These results indicate that the PTPN22 1858C-->T polymorphism does not appear to play a major role in IBD predisposition in our population.