The button mushroom Agaricus bisporus commercially cultivated requires 16-19 degrees C during the fruiting period. Wild strains are also present in natural habitat, and in light of their wide range of geographic distribution reported, from boreal region to tropical region, questions on the development adaptation to temperature arose. Isolates from various geographic areas were screened for their ability to fruit at higher temperature (FHT ability) than commercial cultivars. The FHT trait discriminated at the varietal rank. Agaricus bisporus var. eurotetrasporus was unable to develop any sporophores whilst A. bisporus var. burnettii adapted perfectly to 25 degrees C for fruiting, suggesting that the FHT ability is a fixed trait in these varieties. In contrast, FHT ability of A. bisporus var. bisporus appeared variable and correlated neither with climate/microclimate nor with habitat. However, FHT ability taken as a whole appeared higher in North American populations than in European ones. Some A. bisporus var. bisporus isolates revealed a good potential for cultivation at 25 degrees C.