The performances of 1 g h-' and 20 kg h-' flash pyrolysers are compared for three Australian coals: Loy Yang brown coal (Victoria), Liddell bituminous coal (New South Wales), and Millmerran subbituminous coal (Queensland). The two reactors gave comparable yields of tar, char and Cl-C3 hydrocarbon gases over a range of operating conditions for each particular coal. The yield of total volatile matter from Millmerran coal was similar from both reactors, as were the compositions of chars from Loy Yang coal and tars from the Liddell and Millmerran coals. For Millmerran coal, the yields of tar, Cl-C3 gases and volatiles from the large reactor below 65O"C, were slightly lower than for the small reactor, possibly owing to a shorter retention time of Millmerran coal particles in the large-scale reactor. At a temperature near 600°C tar yields were independent of tar concentration in the effluent gas, over a range 0.0025-0.1 kg me3 for Liddell coal, 0.005-0.26 kg rnF3 for Millmerran coal and 0.0045-0.09 kg mm3 for Loy Yang coal. The tar yields from Millmerran and Liddell coals at 600°C in the large reactor, correlate directly with the atomic H/C ratio of the parent coal, in the same manner as that found for a wider range of bituminous coals in the small-scale reactor.