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 n bean residue. These result confirm that the choice of substrate determines the Biological efficiency values of mushrooms.