Abstract: In this process for the preparation of ketene by the thermal, catalytic cracking of acetic acid under reduced pressure, the hot cracked gases are cooled to approx. 0.degree. to -10.degree. C. and, in the course thereof, water, unreacted acetic acid and acetic anhydride are condensed. The quantity of acetic acid employed for the thermal cracking reaction should be 0.5 to 2.5 t.times.hours.sup.-1 .times.m.sup.-3, relative to the volume V of a shell-and-tube heat exchanger through which the cracked gas is passed. The pressure drop in the tubular heat exchanger should be 50 to 150 mbars and the surface/volume ratio should be 60 to 120 m.sup.-1.