Abstract: Objective: To make comparison among 4 methods for detecting L-form of Mycobacterium tuberculosis and to study its clinical significance in patients with multidrug resistant pulmonary tuberculosis.Methods: Acid-fast sputum smear,modified L J culture,L-form culture and PCR technique were conducted in 103 cases of multidrug resistant pulmonary tuberculosis(MDR PTB).Results: The positive rate of L-form culture was higher than that of acid-fast sputum smear,modified L-J culture,and PCR(P<0.01 to P<0.005).Conclusions: Sputum culture for L-form of Mycobacterium tuberculosis can raise the detected positive rate and facilitate early rapid diagnosis.The infectious rate among patients with MDR PTB is much high,which simultaneously is an important cause of recurrence and aggravation of tuberculosis.