A study was made of the clinical efficacy and immune status in 40 children with chronic osteomyelitis of long tubular bones. Of these, 13 patients received antibiotics endolymphatically and 27 patients were given conventional antibiotic therapy (intramuscularly, intravenously). In view of the predominance of the staphylococcal flora, endolymphatic therapy included the use of gentamycin and lincomycin, the treatment course lasted up to 10 days. Endolymphatic antibacterial therapy has been demonstrated to produce a beneficial clinical effect there was a decrease in fever duration, the amount of postoperative complications, and the duration of inpatient treatment. After endolymphatic therapy the patients' blood manifested a more remarkable, as compared to the control group, rise of the absolute count of T lymphocytes, "active" population of T lymphocytes, together with an increase of the functional activity of lymphocytes in blast transformation, and a reduction, to an equal degree, of the neutrophil and monocyte counts, attesting to a decline of antigenic load of phagocytes. In patients who received antibiotics endolymphatically, the general blood analysis showed a decrease of neutrophilia and marked lymphocytosis. All this mirrored the intensity of immunity activation.