The energy policy of both Europe and Spain considers biomass to be the renewable energy source with the greatest possibilities of growth, from both the point of view of forestry and energy crops. One alternative to energy crops is the use of rapeseed oil as the fuel in thermic processes. This paper studies the use of rapeseed oil and diesel oil mixtures as the fuel for producing heat in a conventional diesel installation. The paper is set out as follows: a) Characterization of the properties of rapeseed oil as fuel and of diesel oil, as well as the mixtures of both. b) Selection of the mixtures according to their physical-chemical properties and to how they adapt to a conventional installation consisting of a mechanical pulverization burner, c) Experimentation with the selected mixtures in a conventional combustion installation, allowing the main combustion parameters to be measured. d) A study is carried out of the yield of the combustion. The conclusions show that the use of rapeseed and diesel mixtures for producing heat energy in conventional equipment is feasible. (c) 2005 Elsevier B.V. All rights reserved.