Abstract For more than half a century, a large number of scholars have endeavored to delineate the effects of temperature on two-phase relative permeability curves using different oils and porous media. However, we still cannot predict how the relative permeability will change with temperature in a specific rock-fluid system. In fact, even a cursory review of the literature on the effect of temperature on oil/water relative permeability will show that a bewildering array of conflicting results have been reported. These inconsistent results are partly due to the likelihood that the effect of temperature is different in different rock-fluid systems and partly due to differences in the measurements techniques that can introduce varying experimental artifacts. The main objective of this study was to see whether some of the contradictions in the reported results would be resolved by examining the effects of temperature on relative permeability separately in different classes of rock-fluid systems. Another objective was to develop empirical correlations for estimating the value of oil/water relative permeability in different systems at higher temperatures. Reported results from a large number of experimental studies of the effect of temperature on relative permeability were collected to generate a large dataset of oil/water relative permeability curves. This dataset was partitioned into four parts representing four different classes of rock-fluid systems, namely: 1) light oil in unconsolidated sand, 2) heavy oil in unconsolidated sand, 3) light oil in consolidated sandstone and 4) heavy oil in consolidated sandstone. The effect of temperature on irreducible water saturation, residual oil saturation, the endpoint relative permeability to oil and water and the generalized Corey saturation exponents of oil and water were analyzed separately for each rock-fluid system. It was found that, although the scatter in reported data is large, some discernable differences are present in the effect of temperature in different rock fluid types. Separate correlations, in the form of generalized Corey saturation exponent model with temperature dependent parameters, were developed for oil/water relative permeability in different rock-fluid systems.