Abstract: This invention relates to freeze-drying of particles of material, for example biological, pharmaceutical and food products.Ordinarily the apparatus used for this purpose has comprised at least one rotary sublimation enclosure each fitted with at least one agitating vane which normally operates about a horizontal axis, but this produces certain disadvantages. According to the present invention, in addition to this vane which is adapted to form a catchment trough when passing through a lower zone of the enclosure and a chute emptying into an axial discharge zone when it ascends, there is provided a cylindrical set of longitudinal vanes which continue on from this agitating vane. Means are also provided for transferring particles from the cylindrical set of vanes to the agitating vane which forms the catchment trough and discharge chute.