In order to identify a gene(s) susceptible to idiopathic pulmonary fibrosis (IPF), we conducted a genome-wide association (GWA) study by genotyping 159 patients with IPF and 934 controls for 214 508 tag single-nucleotide polymorphisms (SNPs). We further evaluated selected SNPs in a replication sample set (83 cases and 535 controls) and found a significant association of an SNP in intron 2 of the TERT gene (rs2736100), which encodes a reverse transcriptase that is a component of a telomerase, with IPF; a combination of two data sets revealed a p value of 2.9×10⁻⁸ (GWA, 2.8×10⁻⁶; replication, 3.6×10⁻³). Considering previous reports indicating that rare mutations of TERT are found in patients with familial IPF, we suggest that the common genetic variation within TERT may contribute to the risk of sporadic IFP in the Japanese population.