Beulah-Zap lignite and Wyodak-Anderson coal (-100 and -20 mesh from the Argonne Premium Coal Sample Program) were dried in nitrogen under various conditions of temperature (20-80 degrees C), gas flow rates (20-160 cm(3)/min), and sample sizes (20-160 mg). An equation relating the initial drying rate in the unimolecular mechanism was developed to relate the drying rate and these three variables over the initial 80-85 % of the moisture loss for the lignite. The behavior of the Wyodak-Anderson subbituminous coal is very similar to that of the lignite. The nitrogen BET surface area of the subbituminous sample is much larger than the lignite. The larger area does not lead to a more rapid rate of drying.