Cell free extracts of Thielaviopsis paradoxa grown on L- alanine as the sole source of nitrogen contained L- alanine dehydrogenase that catalyzes the oxidative deamination  of L- alanine to equimolar amounts of pyruvate and ammonia . L- alanine dehydrogenase formation takes place during the logarithmic phase of growth .Maximal growth and enzyme formation were obtained at the 4^th day of growth .The optimum pH for growth and enzyme synthesis was 4.0 . L- alanine dehydrogenase was induced by a great variety of nitrogen sources , but L –alanine , DL- alanine, L-theronine  and ammonium phosphate were the most potent inducers . L-alanine concentration of 2.1 g/ l was found to be optimum for both growth and enzyme synthesis . L- alanine dehydrogenase formation was increased with increasing concentrations of ammonium phosphate in the growth medium ; the optimum concentration was 2.6 g/ l . The effect of different carbon sources and metal salts on growth and enzyme production was studied .