Enhanced phytase yield was attained with the yeast Pichia anomala using response surface methodology. Interactions were studied with three variables., viz. glucose, beef extract and inoculum density using Central Composite Design, Highest enzyme yields were obtained when the glucose and beef extract concentrations in the medium were 2 and 0.5%, respectively. The inoculum density was found to be an insignificant variable, The concentrations of the variables considered to be optimum by 'one-variable-at-a-time' method (glucose 4%, beef extract 1.25%) were actually higher than that actually required for maximum enzyme production. The application of response surface methodology resulted in an enhancement in phytase production and also minimized the cost of production. This is the first report on use of response surface methodology to improve phytase yield by any yeast. (C) 2002 Elsevier Science Ltd. All rights reserved.