This paper presents characterization studies of flash point, kinematic viscosity and refractive index for several biodiesel/ diesel blends. Biodiesel is produced from soybean, corn, olive, canola, almond, grape and peanut oils. Regression equations are presented to estimate the kinematic viscosity, refractive index and flash point of the studied biodiesel and their blends with diesel fossil fuel as a function of the blend composition. Moreover, as viscosity and refractive index measurements are simple, fast and require very small volume of samples, a correlation study for the blends is conducted to estimate the flash point from these two properties. It is shown that when kinematic viscosity and refractive index are both used for the estimation of the blends flash point, the R 2 values are higher than those found using simple correlations.