Estimates of pressure and temperature conditions of metamorphism in the vicinity of three massive sulfide deposits of the Flin Flon – Snow Lake, Manitoba, greenstone belt have been obtained using mineral assemblages in mafic and felsic metavolcanic rocks. The Flin Flon area around the Centennial deposit, in the western part of the belt, has been metamorphosed to low greenschist facies. Near the Spruce Point deposit, in the central part of the belt, the metamorphic conditions are estimated to be of the upper greenschist facies, with a temperature of 475 ± 75 °C at 2.6 ± 1.2 kbar pressure (1 kbar = 0.1 kPa). The Snow Lake area to the west, in the vicinity of the Anderson Lake deposit, has been metamorphosed to sillimanite grade. In the staurolite–biotite–sillimanite zone, the temperature and pressure conditions were 580 ± 25 °C and 5.25 + 0.75 kbar; in the biotite–sillimanite–almandine zone, the temperature was 620 ± 25 °C at a maximum pressure of 6.2 kbar. Based on the temperature and pressure estimates from the Snow Lake area, it is suggested that experimental studies of the upper stability of staurolite and quartz at low pressure indicate temperatures that are unusually high compared with those indicated by field assemblages.