The reactivity towards liquefaction of a Kentucky ♯9 seam coal and its extrudate (from the Jet Propulsion Laboratory’s 1.5‐inch coal extruder) was measured in a micro‐autoclave. A glass lined 10‐cc reactor was designed so that gas pressure and reactor temperature could be monitored continuously. The use of a fluidized sand bath furnace, relatively coarse mesh coal, and reactor geometry designed to promote ebullient mixing, provides highly consistent results without mechanical agitation. Conversion reproducibility for all runs has been better than ±2%. The thermomechanical history of the extrudate (about 1 min at 425°C) has only a slight effect upon reactivity: coal and extrudate afford similar conversion curves at 435°C, with maxima at less than 15 min. Conversions of coal and extrudate calculated on the basis of fixed carbon are virtually identical.