Studies were carried out to screen the industrial strain HK35 of Pleurotus ostreatus for its ability to develop fruiting bodies in solid state cultivation using several substrates containing 17.8 to 55% coffee grounds. Our results showed that only 55% of coffee grounds was used in the substrate without detecting changes in fruiting body or on its biological efficiency of production. The chemical analysis of the caffeine in the substrate showed that this compound decreased about 59% of the mycelium activity, and no caffeine was found in fruiting bodies indicating its degradation by the fungal strain tested.