Abstract: The present invention relates to the treatment of potato tubers so as to reduce bacterial and other diseases therein and improve the keeping properties thereof.The invention relates to a method comprising the steps of size-grading G potato tubers (55) and then bringing substantially soil-free size-graded tubers (55) to a thermal treatment zone T in which they are immersed in a fluid (10) at a temperature of from 45.degree. to 85.degree. C., for a period of time sufficient to kill at least some microorganisms without significantly damaging the tubers. According to the invention the tubers (55) are then passed substantially directly, through a drying zone D, in which they are surrounded by a hot air flow (68) having a temperature of from 40 to 75 degrees C., to dry their outer surfaces following which they are brought to a cooling zone P.