Myrcene (7-methyl-3-methylene-1,6-octadiene) binary copolymers with styrene, methyl methacrylate or p-fluorostyrene were synthesized. Polymer compositions were measured by H-1-NMR and reactivity ratios were calculated using a nonlinear least squares error-in-variables method. For myrcene-styrene copolymerizations the polymer radicals have a marked preference for myrcene monomer. In the case of the myrcene-MMA copolymerization the growing polymer chains prefer to add the other monomer, i.e. the crossover reaction dominates. The same is true for the myrcene/p-fluorostyrene copolymerization, although the myrcene radical has a higher preference for myrcene monomer in this copolymerization than it does in the myrcene-MMA copolymerization.