Aspergillus ficuum TUB F-1165 and Rhizopus oligosporus TUB F-1166 produced extra-cellular phytase during solid-state fermentation (SSF) using polystyrene as inert support. Maximal enzyme production (10.07 U/g dry substrate (U/gds) for A. ficuum and 4.52 U/gds for R. oligosporus) was observed when SSF was carried out with substrate pH 6.0 and moisture 58.3%, incubation temperature 30 degrees C, inoculum size of 1.3 x 10(7) spores/5 g substrate, for 72 h for A. ficuum and with substrate pH 7.0 and moisture 58.3%, incubation temperature 30 degrees C, inoculum size of 1 x 10(6) spores/5 g substrate for 96 h for R. oligosporus. Results indicated scope for production of phytase using polystyrene as inert support.