Alpha-amylases find a wide-range of applications in industrial processes. They are used to liquefy and saccharify starch in food industry, to soften textures in clothing, and also in detergent formulations. We are characterizing a mildly acidophilic and thermotolerant extracellular amylase from Bacillus sp. Bacterial spores were activated in LB medium and grown at 30^oC in 250 ml Erlenmeyer flasks, at 125 rpm. Cell passages were done at 72 h intervals. Starting from 1l of medium the cells were harvested by spinning at 10000g x 10 min at 4^oC, and the supernatants stored at 4^oC. Protein in the supernatant was thereafter precipitated by slow addition of 62.5% ammonium sulfate at 4^oC. The samples were stored overnight at 4^oC and then centrifuged again at 10000g x 10 min. The precipitate was re-suspended in 5-20 ml of 10 mM Tris-Cl (pH 7.4). With this procedure, the amylase was concentrated 50 to 200-fold. Amylase yield was estimated as 10 mg per ml of culture medium. Amylase activity was assayed by the reaction of the reducing sugars with the dinitrosalycilic acid (DNS) method upon hydrolysis of starch in medium composed of 0.4 M NaCl, 20 mM buffer at different pHs, 0.1% soluble starch, 1 mM Ca2+ or 1 mM EGTA, with no further additions. Otherwise, activity was assayed by hydrolysis of the synthetic substrate pNP-maltopentaoside. The M.W. of the amylase was estimated as 55000 kDa by 10% SDS-PAGE. Production of the enzyme was not induced by addition of glucose, sucrose, starch, Ca²⁺ or Zn²⁺ to the culture medium. The enzyme presented the optimal pH of 5.0-5.5 for activity. This amylase activity depended of the presence of Ca²⁺, and was activated by further addition of 0.4 M NaCl, while 0.4M KCl was marginally inhibitory. The activity was high and sustained over 90 min at 65^oC, while at 75^oC activity was maximal but decayed rapidly with visible precipitation. No activity was detected by assays of hydrolysis of pNP-maltopentaoside, suggesting that the enzyme acts as an endoglucanase. It is believed that this enzyme can find application in industry due to its relative thermotolerance and its mild acidophilic behavior.