To correlate the clinical characteristics with mutations of the STK11 and FHIT genes in 16 patients with Peutz-Jeghers syndrome (PJS). Potential mutations in the coding regions and flanking sequences of the STK11 and FHIT genes were detected with PCR and Sanger sequencing. Of the 16 patients with PJS, 8 had novel mutations in the coding region of the STK11 gene, 1 had a previously reported mutation. 1 carried a mutation in the exon 10 of the FHIT gene, which is a non-coding region. None of the mutations was detected in the immediate family members. None of the patients with STK11 gene mutations had mutation in the FHIT gene. The mutation rate of the STK11 gene among patients with PJS was 56.25%. Mutations of the STK11 gene are the major cause of PJS. Few such patients had mutations of the FHIT gene. Mutations of the FHIT gene may play a part in the pathogenesis of PJS.