Finely resolved C-13 NMR spectra of atactic and isotactic-rich polyacrylonitriles were determined. Assignments of nitrile carbon spectra with pentads were quantitatively confirmed. Methylene carbon spectra were assigned with hexads. Radically obtained polymer obeyed Bernoullian statistics. The polymerization mechanism of isotactic-rich polymer obtained from urea-canal complex is complicated and both the first and the second-order Markov statistics do not hold. The chemical shifts of nitrile carbon signals moved considerably toward up-field as the temperature is raised, due to change of solvation.