Gentamicin producing strain of Micromonospora echinospora was treated with chemical mutagens like EtBr and MNNG and physical mutagens such as UV was carried out to obtain a mutant with enhanced production of gentamicin. After inducing mutations screening for penicillin and kanamicin resistant mutants was done. M. echinospora EtBr-22 strain was obtained by mutations and its gentamicin production in shake flask reaches 1354 mg l(-1) which is 1.53-fold higher than that of the parent strain. Application of different stress conditions like heat shock, feeding high ethanol and high NaCl concentrations during fermentation has found to be effective for the increased production of gentamicin. Production of gentamicin was increased to 1.26-fold in medium supplemented with 0.6% NaCl to 48-h-old culture. (c) 2007 Published by Elsevier Ltd.