Factors that affect to the proposed mechanisms that produce the double yield phenomenon in semicrystalline polymeric materials were studied. The systems under study were ternary blends of low-density polyethylene (LDPE), linear LDPE (LLDPE) and ethylene propylene diene (EPDM). The influence on the yield mechanisms of the following different factors were analysed : processing conditions, composition, stretching rate, cooling conditions and different types of elastomers. The behaviour of these blends in the region where the double-yield points occur was found to be different for those LDPE-rich blends from those LLDPE-rich ones. These differences are explained in terms of the two mechanisms in the double yield phenomenon; that is, the slip of the crystalline blocks and the shear on the crystalline blocks. The stretching-rate effect is explained in terms of the stress relaxation time. The effects of EPDM content, cooling conditions and type of EPDM are found to be equivalent to a smaller stretching rate.