The approximate rate constants for 5-exo and 6-exo cyclizations of alkyl radicals onto oxime ethers have been kinetically determined to be 4.2x10(7) s(-1) and 2.4x10(6) s(-1) at 80 degrees C, respectively. The competition studies gave similar results, confirming the effectiveness of rate constants obtained from kinetic studies. (C) 1997 Elsevier Science Ltd.