Bacterial chaperones were coexpressed to enhance the production of soluble human TNF-alpha and its low-toxicity mutant in Escherichia coil. In the absence of chaperones, about 65% of wild-type TNF and 35% of mutant TNF having a deletion of N-terminal 7 amino acids and substitutions of Leu29-->Ser, Ser52-->lle and Tyr56-->Phe, were produced as a soluble form. In the presence of overproduced chaperones, most of wild-type and mutant TNF (>95%) were produced as a soluble form, indicating that GroEL and GroES chaperones promote folding and assembly of trimeric TNF-alpha. Bacterial chaperones could be useful in the production of TNF-alpha and its variants as well as other proteins with biological importance.