On the basis of the demonstrated superio r ity of the tetracycline-novobiocin combined regimen to staphylococcal infections in vitro and in vivo, the effectiveness of this regimen on the gram negative bacilli infections of the urinary tract was examined on clinical observation of 17 traumatic paraplegics. A daily doses of tetracy c line 500 mg along with Novobiocin 500m g was administered orally for 6 days in every case, and bacteriological urinalysis was performed before and the second day after the treatment. The effectiveness of the therapy was discussed on the bacteriologic cure rate. The bacteriolog i c cure rate on the 2nd day after the treatment with sensitive antibiotics in conventional dose was about 30% in our clinic. The cure rate in the sensitive groud of 2 drug regimen (4 cases out of 17) was 50%, while in the resistant group (13 out of 17) it was 30%, and totally was 35.3%. These results, therefore, suggest the clinical usefulness of the combined therapy with tetracycline and novobiocin on chronic infections of the urinary tract.