1. In a study of the frozen-section diagnoses of 175 exploratory operations on lesions suspected of being tuberculous, the clinical preoperative diagnosis was found to be correct in 74 per cent. of the cases.
2. The frozen-section diagnosis agreed with the paraffin-section diagnosis in 84 per cent. of the cases.
3. Guinea-pig inoculation corroborated the diagnosis in 84 per cent. of the cases.
4. Of thirty-two cases thought to be tuberculous before operation, but proved by sections not to be, the frozen-section diagnosis was correct in 84 per cent.
5. Of thirteen cases thought not to be tuberculous before operation, but later proved tuberculous, the frozen-section diagnosis was correct in 69 per cent.
6. Of the 175 cases, 116 had a final diagnosis of tuberculosis and the frozen-section diagnosis had been the same in 77.5 per cent; fifty-nine cases had a final diagnosis other than tuberculosis and in these the frozen-section diagnosis had been right in 91.5 per cent.
7. Of the 175 cases, the frozen-section diagnosis agreed with the final diagnosis in 82 per cent.