Transition state structures were calculated for A and M routes of ${omega}$-alkenyl radical cyclization (n = 2∼4) using MINDO/3-RHF method. Results of our analysis of HOMO level changes indicated that the transition state stability is not controlled by the decoupling effect alone as Bischof suggested, but in greater degree it is determined by through-bond interaction of the HOMOs with the framework $HO-{sigma}$ or $LU-{sigma}^*$ orbitals. In case of larger n (n > 4), the product stability was considered to be the main cause of M route dominance in the cyclization.