Nine novel cyclodextrin glycosytransferase-producing bacteria were isolated from soil in a low acidic pH (3-4) medium at high temperature (45-60C). The isolated acidophilic bacteria were identified as Bacillus acidocaldarius. Highest yield of enzyme was obtained by using the following medium: 4% raw potato, 1% peptone, 0.1% yeast extract, 0.02% (NH4)2SO4, 0.05% MgSO4, 0.02% CaCl2, 0.3% KH2PO4. The crude enzyme showed a very broad pH-activity curve and had two optium pH ranges at 30 and 5.0-6.0. The crude enzyme was most active at 90C.