Large-scale exploitation of the potential benefits of ectomycorrhizal fungi in improving plantation yields means that fermentation techniques for these fungi will be required. Starting with a base performance on a rich, complex medium, the effect of variations in some physicochemical culture parameters on biomass yield was studied. It was possible to reduce the amount of phosphate salts (to 1/9th) and other ingredients (to 1/3rd) in the medium. A shaking speed of either 100 rpm or 200 rpm in an orbital incubator was satisfactory and biomass yield responded to an increase in carbon substrate (glucose, from 10 g l(-1) and 20 g l(-1)) though Y-x/s declined. An increase in inoculum size shortened culture time but decreased biomass yield. The upper limit of the incubation temperature was between 25 degrees C and 30 degrees C. Biomass yields were about 12 g l(-1) dry weight (Y-x/s = 0.63) when 20 gl(-1) glucose was supplied, and about 7 gl(-1) (Y-x/s = 0.74) when 10 g l(-1) glucose was supplied.