An alkaliphilic and highly thermostable alpha-amylase producing Bacillus sp. was isolated from Van soda lake. Enzyme synthesis occurred at temperatures between 25 degrees C and 40 degrees C. Analysis of the enzyme by SDS-PAGE revealed a single band which was estimated to be 66 kDa. The enzyme was active in a broad temperature range, between 20 degrees C and 90 degrees C, with an optimum at 50 degrees C; and maximum activity was at pH 10.5. The enzyme was almost completely stable up to 80 degrees C with a remaining activity over 90% after 30 min pre-incubation. Thermostability was not increased in the presence of Ca2+. An average of 75% and 60 degrees C of remaining activity was observed when the enzyme was incubated between pH 5 and 9 for 1 h and for 2 h, respectively. The activity of the enzyme was inhibited by SDS and EDTA by 38% and 34%, respectively.