Comparative Study of Fruiting Body Production of some Oyster Mushroom in Two Different Temperatures Oyster mushroom (Pleurotus spp.) are widely cultivated throughout the world for nutritional as well as for medicinal purposes. To see the effect of temperature on yield, efficiency and protein content of different oyster mushroom, eight oyster mushroom i.e. Pleurotus ostreatus, P. florida, P. sajorcaju, P. eryngii. P. pulmonarius, P. citrinopileatus, P. flabellatus and P. fossulatus were taken. 10% spawn of respective mushroom strains were inoculated in overnight wetted non-sterilized rice straw and kept in two different temperatures (18°C and 25°C). In 18°C all the species produced fruiting bodies whereas in 25°C, all the tested species except P. fossulatus could produce the fruiting bodies. Considering the time as a main factor in fruiting, a new parameter Biological efficiency day-1 (BED) is introduced to better understand the fruiting efficiency in respect to time. It was found that beyond second flushes fruiting was not commercially sustainable. In lower temperature (18˚C) P. florida (ITCC 3308) showed the highest BED value whereas P. pulmonarius showed the highest BED value in higher temperature (25˚C). The protein content of the fruiting bodies varied significantly from species to species though temperature has no such effect. The fruiting life varied from 4-7 days in all the tested mushrooms except P. fossulatus which was much longer (>25 days). In present experimental condition P. fossulatus showed the most temperature sensitivity, P. pulmonarius showed the least temperature sensitivity whereas all the other species showed moderate temperature sensitivity.