The ectomycorrhizal fungus Pisolithus tinctorius was grown in vitro with different concentrations and combinations of three different sodium salts viz., sodium chloride, sodium sulphate and trisodium citrate (NaCl, Na2SO4 and Na3C6H5O7) for 30 days. At the end of the experiment the mycelial biomass and protein content of the fungus was evaluated. Based on the salts tested the combination of NaCl and Na2SO4 in optimum concentrations actually promoted the growth of P. tinctorius. Box-Behnken design with three variables like NaCl, Na2SO4 and Na3C6H5O7 was used to identify a significant correlation between the effect of these variables on mycelial biomass production. The experimental values are in good agreement with predicted values, the correlation coefficient being 0.9880.