Peutz-Jeghers syndrome is a rare hereditary syndrome characterized by presence of hamartoma polyps in intestinal tract and usually by mucocutaneous pigmentation. Clinical-genetic characteristics of Russian patients with Peutz-Jeghers syndrome were studied for the first time. Four germline mutations in STK11gene were found in probands from six families and three of them had not been described previously. Clinical pattern of disease in Russian patients included: frequent polyposis of colon and stomach (62,5% and 75%, respectively) along with small bowel; frequent presence of malignant tumors (62,5%). These clinical aspects can help physicians to find out Peutz-Jeghers syndrome. Molecular-genetic testing of individuals should be recommended.