It has been reported that there is a relationship between a single-nucleotide polymorphism (SNP) in the promoter region of the CD14 gene at position -159 (C→T) and infectious diseases. The aim of the present study was to test the hypthesis that expression of this SNP correlates with periodontal disease in a Japanese population. The CD14 genotype was determined in 163 subjects with periodontitis and in 104 age- and gender-matched control subjects without periodontitis. The genotype distribution and allele frequency within the periodontitis patients were not significantly different from those of control subjects. There was, however, a significant difference in the genotype distribution between young patients (< 35 yrs) and older patients (≥ 35 yrs). These findings suggest that CD14 -159C/T polymorphism is not related to the development of periodontitis in a Japanese population, but that, within the periodontitis subjects, expression of the SNP may be related to early disease activity.