Pleurotus ostreatus var columbinus was cultivated on two kinds of perlite-defined substrates (PDS). rn a first experiment, PDS with either cellulose, sugar nitrogen or mineral-starvation were tested using pure washed mycelium as inoculum in reference to grain spawn and compared with a wheat-straw substrate. Cellulose, nitrogen and minerals were found to be essential compounds for Pleurotus fruiting. When grain spawn was used as inoculum, nitrogen and minerals supplied by the grain were sufficient for fruiting, in spite of nitrogen and mineral-starvation. Protein content of fruitbodies increased when grown on PDS inoculated with spawn only. In a second experiment, PDS as synthetic substitutes for wheat straw and grass hay were inoculated with pure washed mycelium and compared to natural substrates. In spite of mineral and sugar supplement, synthetic substitutes for wheat straw gave a fruitbody yield lower than that recorded on natural wheat straw. The protein content of fruitbodies harvested from all substrates did not vary.