A process and apparatus for drying or heating a particulate material by means of heat transfer media which is brought into direct contact with the particulate material within a continuously rotating cylindrical drum. The particulate material flows in one general overall direction through the drum and the heat transfer media flows in a generally opposite direction through the drum. The particulate material is subjected to heat treatment by repeatedly coming into direct and immediate physical contact with the heat transfer media in the course of flowing through the drum while it is subsequently separated from the heat transfer media per revolution of the drum.