The linear viscoelastic properties of two types of olefinic thermoplastic elastomer blends were studied using dynamic Theology. The first type consists of a blend of PP, SEBS and oil and has a co-continuous morphology. The second type consists of vulcanised EPDM particles dispersed in a PP matrix. The dynamic Theological behaviour of the blends is a weighted contribution of the properties of the two individual phases. In both blend types, the storage modulus at low frequencies can be correlated to the properties and morphology of the elastomer phase. With increasing PP or oil content in the blend the value of the modulus at low frequencies are reduced. The mechanical models of Coran and Veenstra are able to describe the dynamic moduli. An additional parameter was included to determine the oil concentration in the two phases. The model parameters are correlated to the composition and the morphology. (C) 2004 Elsevier Ltd. All rights reserved.