The imbedded-fiber retraction (IFR) method was used to study the effect of temperature and PDMS molecular weight on the interfacial tension of PS/PDMS blends. The interfacial tension decreased with increasing temperature and analysis of the temperature dependence using a simple linear fit gave -dgamma/dT value of 0.058 +/- 0.010 dyn/cm-deg. Reported -dgamma/dT values of PS/PDMS blends are highly dependent on the molecular weights of the polymers and can have values that are < 0, 0, or > 0. Our interfacial tension values were independent of the molecular weight of PDMS and this was attributed to the molecular weights studied here being well above the entanglement values of both polymers. However, analysis of interfacial tension data from this work and the literature showed the following empirical relationship between apparent blend molecular weight, M-b, and interfacial tension of PS/PDMS blends with a correlation of 0.94: gamma(12) = gamma(0) + k(2)M(b)((-2/3)) , where gamma(0) = 7.3 +/- 0. 3 dyn/cm ; k(2) = -517 +/- 41 (dyn/cm)(g/mol)(2/3).