The third edition of the manual (the previous ones were published in 2001, 2006) has been revised and expanded. The book presents the fundamental principles of modern clinical dietetics in combination with a presentation of the clinical features of the course of diseases and pathological processes. The book is based on the author’s own experience, as well as the latest achievements in domestic and foreign dietetics. The content of the publication combines scientific aspects of nutrition for a sick person and practical recommendations for the use of diet therapy in specific situations of organizing therapeutic nutrition not only in hospitals, but also in outpatient settings. For nutritionists, gastroenterologists, therapists and senior students of medical universities.