Energy efficiency in the production and transportation of different kinds of biomass in Sweden has been analysed, as well as the change in energy efficiency in a transition from fossil-fuel-based to biomass-based systems. Net energy yields under current production conditions were found to be highest for short-rotation forest (Salix) and sugar beet (about 160 to 170 GJ ha-1 year-1), followed by ley crops (110 to 140 GJ ha-1 year-1), and rape, wheat, and potatoes (50 to 90 GJ ha-1 year-1). The energy input per unit biomass produced is lowest for straw, logging residues and Salix, equal to 4 to 5% of the energy output. Corresponding figures for perennial ley crops are 7 to 10% and for annual crops 15 to 35%. Salix chips can be transported by truck about 250 km before the transportation energ is equal to the production energy. Corresponding distances for tractor, train and boat (coastal shipping) are about 100 km, 500 km and 1000 km, respectively. It is estimated that future increases in yield and technological development will almost double net energy yields for dedicated energy crops within the next two decades. A transition from a fossil-fuel-based energy system to a CO2-neutral biomass-based system around the year 2015 is estimated to increase the energy input in biomass production and transportation by about 30 to 45%, resulting in a decreased net energy output of about 4%.