Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Methyl ester biodiesels from vegetable oils, including soy, corn, canola and sunflower, and from swine lard, were prepared. They were mixed with mineral diesel to produce blends from 5% v/v to 50% v/v of biodiesel, i.e., B5, B10, B20 and B50. The flash points of these mixtures, the pure diesel (B0) and the pure biodiesel (B100) were determined. In all cases, it was observed that there was a second order polynomial correlation between the flash point and the percentage of biodiesel in the blend, it was concluded that is possible to estimate the flash point of a diesel-biodiesel mixture if its composition and the flash points of the pure components are known. Quasi-linear correlations between the increase of the flash point and the increase in biodiesel content were observed for B0 to B20 mixtures. If a mean linear correlation is applied, independently of the oil or fat used, in this case where the flash point of the petrol diesel is 40.1 degrees C, the estimated flash points for the blends from B5 to B20 will be approximately 45 +/- 3 degrees C.262 393395Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)