The effects of oc - and f3- cyclodextrin (x - ,13- CD's) on the rates of base cleavage of 4 - CNC6 H4 SnMe3 ,3—CIC6 H4 CH2 MMe3 , 4 C1C6 H4 CH2— MMe3 and 3,5 - CL2 C6 H3 CH2 MMe3 with M = Si and Sn have been examined in H 2O - Me0H medium . oc - and 13-CD's accelerate the cleavage of the RSnMe3 compounds (R=3-0106 H4 CH2 , 4-0106 H4 CH2, and 3,5 - 01 2 C6H3 CH2 ) . There is no significant catalysis in the case of the corresponding silicon compounds.