This paper presents an evaluation of the inˉuence of relative humidity and temperature on the ˉowability of the following food powders: ˉour, tea and whey permeate. These powders were selected because of their dierent physical properties. Powder ˉowability was measured using an annular shear cell in a chamber with controlled relative humidity and temperature. A number of powder physical properties, including particle size distribution, water sorption isotherms and dierential scanning calorimetry(DSC) thermograms, were measured. These properties are used in interpreting and comparing the ˉowability measurements for each powder.