The aim of this study was to develop a systematic quality index for application in the cultivation of Agaricus bisporus (Lange) Imbach mushrooms, based on the physical, chemical and biological properties (indicators) of the compost and casing layers (factors). The relative importance (weight) of each of the factors and indicators, their normalized scores, the quality index values and the correlation with the mushroom yield were evaluated. Three casings (soil + peat moss, Dutch commercial casing, and peat moss + spent mushroom substrate) and two composts were used. The resulting quality index is reliable and useful for identifying problems and can also serve as a rapid tool for possible intervention when problems occur. There was little difference between the two composts used, both of them showing high factor index values. Although the peat + spent mushroom casing presented certain limitations because of its high electrical conductivity, the other two casings showed satisfactory factor index values.