pressurized heated grid apparatus was used to study the pyrolysis yields of volatiles from a wide range of coals and from maceral concentrates of five coals. Samples crushed to a nominal particle size of 1 mm were heated in nitrogen at 1000 K s(-1) to 950 degrees C at a pressure of 2.5 MPa, simulating the conditions of a pressurized fluidized bed gasifier. The pyrolysis yields were correlated with the BS volatile matter figures by the equation: Calculated weight loss(% daf) = 0.943 x VM(% daf) - 5.994 Alternatively, by treating the coals as combinations of macerals, the pyrolysis yields were derived from those of their constituent macerals, with allowance for the variation of vitrinite properties with rank by means of the mean vitrinite reflectance (MVR). The expression: Calculated weight loss(%daf) = 0.158 x (vol% mmf vitrinite)MVR + 0.504 x (vol% mmf liptinite) + 0.427 x (vol% mmf inertinite) was found to give a reasonable correlation for the coals studied, under the conditions of this work.