We investigated the possible association of solute carrier family 6 member 18 (SLC6A18) with hypertension and blood pressure in Japanese, since the homologous murine XT2 gene was recently reported to be associated with hypertension. The entire coding region of SLC6A18 was sequenced in 30 unrelated Japanese subjects. The deleterious effects of the observed nonsynonymous single nucleotide polymorphisms (SNPs) on the phenotype were predicted using bioinformatics software. We tested the associations of one deleterious SNP (Y319X) with blood pressure and hypertension in a general population of 1,004 subjects in one area of Japan. Both quantitative and qualitative analyses adjusting for age and body mass index (BMI) as covariates were undertaken. Four synonymous (P7P, T32T, G37G and V387V), three missense (S12C, I32T and L478P) and one nonsense (Y319X: g1230757 C > G) polymorphisms were found. One of the synonymous polymorphisms was novel (V387V) by reference to the dbSNP database. The Y319X genotype distribution of CC:CG:GG in this population showed frequencies of 0.382, 0.461 and 0.156, respectively, which followed Hardy-Weinberg equilibrium. The nonsense polymorphism had odds ratios of 0.83 (confidence interval [CI] = 0.59-1.15, p = 0.26) in males and 0.96 (CI = 0.72-1.29, p = 0.80) in females with hypertension or current medication for hypertension. For the quantitative analysis, we excluded the current medication subgroup. The nonsense allele was not a significant predictor for systolic or diastolic blood pressure. This is the first report showing that a single polymorphism in SLC6A18 is not associated with hypertension or blood pressure in Japanese.