The serum procollagen peptide (PIIIP) levels of 132 cases of tuberculosis and 37 healthy persons have been detected with RIA. The results showed that the serum PIIIP level in tuberculous patients is significantly higher than that of healthy persons (P < 0.001) and strongly related to the severe degree of activity and the size of pathological change of tuberculosis and patient condition. It suggests that there might be some significance in assessing serum PIIIP in tuberculous patients for evaluating the severity and prognosis of the illness.