This paper presents the results of adiabatic oxidation studies on the propensity of 18 pulverised coals to spontaneous combustion. All the coal samples were tested at an initial temperature of 40 degrees C and three samples at 60 degrees C to mimic the condition in a coal mill. Their propensities to spontaneous combustion were ranked according to their initial rate of heating (IRH) and total temperature rise (TTR) values. The influence of initial temperature, moisture content, particle size and coal ageing on spontaneous combustion were also studied. The results demonstrated that air humidity is an important factor in determining whether a heating will progress rapidly or not. The particle size distribution of the coal affects the IRH and TTR values, with relatively smaller particles tending to be more reactive. Aged and pre-oxidised coals have higher IRH and lower TTR values, and the coal becomes less reactive. The magnitude of the temperature rises (TTR) increases with increasing initial temperature. No direct correlation was observed between the adiabatic oxidation values and the individual coal properties.