Collection Site:-The south western region of Bangladesh is located between 22°55'N latitude and 89°15'E longitudes belongs to Kushtia, Chuadanga, Jessore, Satkhira and Khulna districts and about 9m to 10m above from the sea level. The collection sites were natural forests, university campus, colleges, farms, residential areas, roadside and nearby villages of the above mentioned districts. Experimental Site:-The analytical experiments were conducted in the Laboratory of the Department of Plant Pathology, Sher-e-Bangla Agricultural University (SAU), Dhaka, Bangladesh. Sampling Procedure:-A pre-designed collection procedure and data analysis procedure was applied to collect information on biodiversity, distribution, habitat and morphology of mushrooms from the above mentioned regions of Bangladesh.Collection of Mushrooms:-A detailed survey was carried out in Kushtia, Chuadanga, Jessore, Satkhira and Khulna districts under the south western region of Bangladesh from June to October, 2014 to determine the morphological variability of mushroom’s population following the methodology of Hailing, 1996. Furthermore, the spotted and fleshy mushrooms were minutely inspected, collected and brought to the laboratory for detailed inspection. Morphological Observation during Collection:-The data for the identification of mushrooms were recorded after collection on the following parameters, such as locality, habitat, type of soil, forest type, size of the fructification, carpophores shape, umbo, cap color, cap surface, cap margin, cap diameter, scale, gill color, gill edges, gill attachment, gill spacing, stipe length, width, color, shape, type of veil, annuls (position) and volva (Srivastava and Bano, 2010). Mushroom Processing:-The photographs were taken in different angles and some morphological data, viz. size of fructification, pileus diameter, stipe length and their color were recorded after the collection of mushrooms. Mushrooms were dried and processed following the predefined method (Kim, 2004). Drying:-Collected samples were cleaned and dried by using electrical air flow drier controlling the1000 voltage, which can easily remove the moisture content from the collected mushrooms within 3-7 hours with a regular interval basis power supply (15 minutes switch off and 30 minutes switching) depending on the structure and texture of the species (Kim, 2004). Storage:-Dried mushrooms were stored into a zip-lock type poly bag during the survey period for further studies. Silica gels were used at the rate of 10% of dry basis during the storage period (Kim, 2004).Morphology and Microscopic Characterization:-The basidiocarps were rehydrated by soaking in water for few minutes before analyzing their morphology. Qualitative characters such as color, shape, and presence of hymenia were evaluated by eye observation while texture was determined by feeling the back and top surfaces using fingers. Most of the morphological data were recorded during collection period that is when the mushroom was in fresh form. Permanent glass slides were made from rehydrated basidiocarps with the aid of a sharp surgical blade for the microscopic characterization. Basidiocarps were immersed in cotton blue stain and glycerin and placed on glass slides and covered with cover slips. Furthermore, the spore size was measured using Motic microscope with the magnification of 40x (Svrcek, 2000).The final identification and classification done by comparing the previously recorded characteristics of mushroom following the color dictionary of mushroom written by Dickinson and John (Dickinson and John, 1982), the mushroom guide and identifier by Jorden (Jorden, 2000) and the mushroom identifier by Pegler and Spooner (Pegler and Spooner, 1997).Habitat, Distribution and Diversity Analysis:-The mushrooms were found in an association with various substrata. The surrounding environment, temperature, soil pH, moisture condition and vegetation were recorded for the biodiversity of mushroom. The soil pH and moisture were measured by pH meter. On the other hand, the air temperature was measured by thermometer during the collection. Collected samples were wrapped with poly bag and brought into the laboratory for further study. The distribution of mushrooms on the locality was also recorded. The frequency and density of different species has been determined by the following formulas (Zoberi, 1973).