Serial determinations of proteolytic-enzyme-inhibitor patterns have been most valuable as a therapeutic guide in cases of osteomyelitis of the spine (especially tuberculous osteomyelitis) and in cases of tuberculous bone and joint disease in general. They have frequently been helpful in the differentiation of benign from malignant primary bone tumors, and they have often been used in the follow-up of patients with tumors as a means of confirming the presence of metastases. As a means of estimating the patient's "resistance" to the catabolism present, these methods offer additional information for the surgeon to use in reaching a presurgical judgment.