Phosphatases are ubiquitous enzymes in prokaryotic and eukaryotic organisms that hydrolyze esters and anhydrides of phosphoric acid. They do not show high specificity for any substrate, and are classified as acid phosphatases with pH optimum below 6.0, and alkaline phosphatases with pH optimum higher than 8.0. In this study we optimized the conditions for production of phosphatases by the filamentous fungus Aspergillus ochraceus. The microorganism was grown in liquid medium (Khanna, Adams, Vogel, M5 and SR), under orbital agitation (100 rpm) or stationary condition, at 40ºC, for different times. The enzymatic activity was determined using p-nitrophenylphosphate (p-NPP) as substrate, in 100 mM ampol buffer, pH 8.5 (alkaline phosphatase), or 100 mM sodium acetate buffer, pH 4.5 (acid phosphatase). The production of phosphatases was significantly affected by the medium composition and by the time of growth. The higher levels of acid phosphatase activity were obtained in Khanna medium (72 hours; orbital agitation), supplemented with 1% cassava flour (intracellular enzyme) and 1% oat meal (extracellular enzyme). The production of intracellular and extracellular alkaline phosphatases was maximal in Khanna medium supplemented by 1% cassava flour and in SR medium supplemented by 1% corn meal, respectively. Intracellular and extracellular phosphatases, acid and alkaline, had temperature optima between 50-60ºC and pH optimum of 4.5 for acid phosphatases and 10.0 for alkaline phosphatases. Financial support by FAPESP and CNPq.