The monomer -myrcene, a renewable resource, was polymerized in cyclohexane using two different Ziegler-Natta catalyst systems based on neodymium Nd(Oi-Pr)(3) and NdV3. The Nd(Oi-Pr)(3) was combined with [HNMe2Ph][B(C6F5)(4)] (or [CPh3][B(C6F5)(4)]) and Al(i-Bu)(3) (or Al(i-Bu)(2)H). Next, the NdV3 was activated using Al(i-Bu)(3) and AlEt2Cl. Both catalyst systems exhibited high polymer yields near 100% in the established reaction time, high polymer molecular masses, and broad molecular mass distributions. The catalyst systems gave an effective and stereospecific polymerization reaction of -myrcene providing high cis selectivity of 1,4-polymyrcenes (>92%) with a glass transition temperature between -66 and -62 degrees C. The above-mentioned features of resulting elastomers in conjunction with the polymer's molecular masses and molecular mass distributions proved to be sensitive to borane and alkylaluminum compounds molar ratios, [B]/[Nd] and [Al]/[Nd] using Nd(Oi-Pr)(3) and [Cl]/[Nd] and [Al]/[Nd] with NdV3.