This work presents information concerning problems related to mechanized harvesting of beans, primarily in the aspect of causes of mechanical damage to seeds in the course of bean harvest operations. On the basis of the author’s own studies and of review of literature, the author begins with an analysis of the anatomical and physical features of bean seeds in the aspect of their resistance to mechanical damage under dynamic loads. Next, he presents factors affecting the occurrence of damage to seeds in the process of threshing, as well as characteristics of thresher units used for navy and snap bean threshing. In the assessment of seed resistance to mechanical damage impact loads were primarily taken into consideration, due to the character of operation of threshing units. The effect of geometrical dimensions of seeds, the mass, and the point of force application were analysed. Also analysed was the occurrence of damage with relation to such factors as the speed and multiplicity of impacts, seed moisture, and the material of the impacting element. The work presents also the technologies of bean harvest and an analysis of factors determining the occurrence of seed damage during threshing. It was found that seed damage occurring in the course of threshing depends primarily on the design features of the thresher unit, perimeter speeds of threshing drums, and seed moisture content. The author presents adaptations of beater- and cog-type thresher units of combine harvesters. The adaptations consisted primarily in increasing the screening capacity of thresher unit concaves and in the application of rubber elements in threshing drums. Good bean threshing effects were obtained for a multi-drum finger-type thresher unit (3% – damage to seeds, 2% – non-threshed seed residue). In the work the author presents also thresher units for snap bean grown for dry seeds.