The results of research of technological characteristics of a device with rotating drum are analyzed; this device is used as a separator and mixer in the production of seeds of cereals and small-seeded vegetable crops. The seeds handling is organized by means of the separation effects (segregation and migration) of nonuniform particles during their interaction on a gravity chute. The processes of separation and mixing are performed due to the control of segregated flows in the operating volume of device. It is found that separation effects can be used to organize the cleaning of seeds containing hard-separable impurities, and their calibration on size and density at the same time. During cleaning and calibration of carrot seeds the result of their primary handling was the yield of 65% of cleaned seeds; their mass exceeded by 67% the mass of seeds in primary waste. It is also found that the use of particle interaction effects creates the conditions for seeds handling with their minimal damage. The germination of seeds calibrated in accordance with the proposed technique is higher by 5% than the germination of seeds obtained in traditional way. It is shown experimentally that there is a possibility to organize the process of continuous mixing of seeds with dosed supply of microcomponents, the period of which is much larger than the average retention time. The drum device saves the properties of heat and mass transfer equipment (dryer) in all the variants of its technological applications. The selective and goal-oriented control action on a part of material flow in device provides the technological effects without any significant increase of energy consumption.