For the catalytic and noncatalytic liquefaction of Wandoan and Illinois No. 6 coals with anthracene oil and hydrogenated anthracene oil at 450 degrees C, the two-stage liquefaction with in situ preheat treatment at 250, 350, and 400 degrees C for 15 min gave higher yields of toluene solubles (TS) and hexane solubles (HS) than the one-stage liquefaction without in situ preheat treatment. The effect of preheat treatment at low temperature on the yields of TS and HS is believed to result from the swelling of coal in the solvent. The two-stage Liquefaction is also advantageous from the viewpoint of using a lower preheat temperature than the liquefaction temperature, compared with the one-stage liquefaction for the same reaction time.