An NMR investigation was carried out on variable composition, random and equimolar, alternating copolymers of acrylonitrile (A) with styrene (S), isoprene (I), and butadiene (B). The NMR spectra of the SA copolymers contained peaks at 3 τ (aromatic ring protons), 7.2-7.5 τ (CH protons of A), and 8.1 -8.5 τ (CH and CH2protons of S and CH2protons of A). All NM R peaks of the alternating SA copolymer were shifted to the higher field due to the shielding effect of S. The NMR spectra of the IA copolymers contained peaks at 4.72-4.91 τ (˭CH protons of I), 7.27-7.4 τ (CH protons of A), 7.71-7.93 τ (CH2protons of I), and 8.35 τ (CH3protons of I and CH2protons of A). The peaks at 4.72 τ (˭CH) and 7.72 τ (CH2) were assigned to I in the I-A diad and the peaks at 4.91 τ (˭CH) and 7.93 τ (CH2) were assigned to I in the I-I diad. The NMR spectra of the BA copolymers contained peaks at 4.4-4.6 τ (˭CH protons of B), 7.2-7.5 τ (CH protons of A), 7.71-7.97 T (CH2protons of B), and 8.0-8.4 τ (CH2protons of A). The peaks at 4.42 τ (˭CH) and 7.71 τ (CH2) were assigned to B in the B-A diad and the peaks at 4.6 τ (˭CH) and 7.9 τ(CH2) were assigned to B in the B-B diad. The alternating structure of the copolymers prepared through metal halide-activated complexes was confirmed by NMR analysis. The random copolymers prepared by free radical initiation contain a high concentration of alternating sequences, as anticipated from the values of r1and r2where r1(S, I, and B) is 6-10 times higher than r2(A).