Abstract: A method of and an apparatus for expanding tobacco, particularly tobacco impregnated with solid carbon dioxide are disclosed. The apparatus comprises an arcuate, generally C-shaped duct for conveying the tobacco material in a hot gaseous medium to sublimate the solid carbon dioxide and expand the tobacco. The duct has a non-circular cross-section, preferably a rectangular cross-section, with a high width-to-depth ratio and an increasing depth from the inlet to an intermediate portion of the duct then a decreasing depth from the intermediate portion to the outlet of the duct. A winnower device infeeds the tobacco material into the duct adjacent the throat of a venturi section connected to the inlet of the conveying duct. A tangential separator with an adjustable baffle at the inlet thereof for controlling velocity in the separator is used to separate the expanded tobacco from the gaseous medium.