Two patients, both in the second trimester of pregnancy, received 2 Gm. of streptomycin (0.4 Gm. five times per day) for ninety-five and ninety days, respectively. The blood serum levels ranged between 12 and 25 mg. per cubic centimeter. The first (V. B.) had had a nephrectomy on the right side four years previously, for far advanced caseous renal tuberculosis, and on admission showed evidence of progressive tuberculous involvement of the left kidney and bladder. The second (J. S.) had had primary pleural effusion followed just prior to admission by rapidly progressive far advanced hematogenous pulmonary tuberculosis. In each case streptomycin was felt to offer the only hope for recovery. Because the pregnancies were in the second trimester, it was felt safer to allow them to continue rather than to resort to interruption. At the time streptomycin therapy was started, V. B. was five and and a half months pregnant and J. S. four months pregnant. Both showed improvement during and following streptomycin therapy, though vestibular function was completely lost in each patient. In each case examination of the placenta