Distribution of gentamycin and klaforan in the lymphatic system, blood and cerebrospinal fluid, as well as their effect on lymph node morphology was studied experimentally on 46 dogs. The antibiotics were administered endolymphatically in doses of 1 and 30 mg/kg respectively. The highest levels of gentamycin (200-250 micrograms/ml) and klaforan (up to 1600 micrograms/ml) were detected in the central lymph. The therapeutic levels of the antibiotics in the central persisted for 24 and 72 hours respectively. The antibiotics accumulated mainly in the regional (inguinal and pelvic) lymph nodes, where their high levels were determined for 72 hours. The levels of the antibiotics in the distant (cervical and tracheobronchial) lymph nodes were lower and did not exceed the therapeutic ones. They persisted for 6 and 24 hours respectively. No unfavourable effect of the antibiotics on the structure and cell composition of the lymph nodes was noted. After endolymphatic administration in the above doses the antibiotic levels in the blood serum were close to those observed after administration by the routine routes. After endolymphatic administration in the above doses the antibiotics penetrated into the cerebrospinal fluid.