To study the contribution of the CD14 gene to the pathogenesis of rheumatoid arthritis (RA) in Japanese patients.CD14 genotyping was carried out at the -159C/T dimorphic site in 97 RA patients and 104 normal subjects by the PCR-RFLP (restriction fragment length polymorphism)HLA-DRB1 genotyping was performed by the PCR-SSCP (sequence specific conformational polymorphism) method.The -159C/T dimorphism is not associated with whole RA or with female RA, and the results were compatible with a previous report from Germany. The -159C/T dimorphism was not associated with rheumatoid factor (RF)-positive RA, although the -159T allele tended to be associated with RF in the German report. The -159C/T dimorphism showed no association even in RA patients with the RA-susceptibility HLA-DRB1*0405. The -159T allele was prevalent in Japanese controls.The CD14 gene is very unlikely to be genetically involved in the pathogenesis of Japanese RA.