The highest Biological efficiency was obtained for mushrooms cultivated in substrate enriched with 12.7 mgkg1 of Se. This Biological efficiency was higher than that observed for Pleurotusmsajor-caju cultivated in maize straw and in cotton residues. However, it was lower than when this fungus was cultivated in bean residue. These result confirm that the choice of substrate determines the Biological efficiency values of mushrooms.