Seveeral kinds of starch were used to be substrate for CGTase from Bacillus circulans A11 It was found that potato and sago starch gave the highest yield. Rye gave the lowest yield. For cassava starch, the yield was 37% and ratio of α -, β -and y-CD was 2.8:3.7:1.0 Amylopectic was the better substrate for CGTase than amylase. However, no direct correlation between the amylase and amlopectin contents with % CD yield. To study cassava starch was used as substrate for CGTase, Using gelatinized cassava starch, the optimum condition for total CD and β -CD was incubating 500 U/g starch with 2.5 g% cassaca starch for 8 hrs at 40℃. The total CD yield was 35 % and α: β y-CD ratio was 1:2.76: 1.66 For α -CD production, the optimum condition was 2.5 g% of cassaca starch, CGTase 1,250 U/g starch at 400C for 16 hrs. Total CD yield was 35% and α: β:y-CD ratio was 10.8:12.7:1.0. For starch liquefication step prior to CGTase catalysis, the best condition per gram starch was respective treatment with 96 U pullulanase for 24 hrs and β -amylase 0.0024 U for 20 min. Study on the size of substrate for cyclodextrin production showed that DP 9 fraction from partially purified β -amylase treated cassava hydrolysate gave the highest total CD with β -CD as the major product. Alpha was the major product if fractions of DP 20-82 were used. In addition, DP 26 fraction from partially purified pullulanase treated cassava hyfdrolysate gave the highest total and β -CD yield. The DP 75 farction gave more than β -CD but the total yield was considerable less (27% vs 9%). Moreover, addition of complex ant into the CGTase reaxction mixture was observed. The result obtained indicated that the degree of enhancement and the ratio of a: β y-CD varied with kind of complexant, enzyme concentration and time of incubation. The optimum condition for α -CD production was incubvation of 2.5 g% gelatinized starch with CGTase 500 U/g starch in the presence of 20% (v/v) ethanol for 36 hrs at 400C or with 1,500 U/g starch without any addition of complexant at the same incubation condition. The optimum condition for β-CD production was incubated with CGTase 500 U/g starch and 20% (v/v) 2-butanol at the same incubation condition on α-CD production. The optimum condition for y-CD production was incubated with CGTase 50 U/g starch in the presence of 20% (v/v) ethanol at the same incubation condition α -CD production.