The importanc e of economica l productio n of agricultura l materials , especially crops and anima l product s serving as base material s for foodstuffs , and of their technologica l processing (mechanica l operations , storage , handling , etc.) is everincreasing . During technologica l processes agricultura l material s may be exposed to variou s mechanical , thermal , electrical , optica l and acoustica l (e.g. ultrasonic ) effects. To ensur e optima l design of such processes , the interaction s between biological material s and the physica l effects, acting on them , as well as the genera l laws governing the same, must be known. The behavior of most agricultura l material s deviates essentially from tha t of the generally known elastic materials . The flow propertie s of cereals , of granular material s and of those material s which fall into the category of non-Newtonian liquids , also deviate essentially from the correspondin g ideal liquid behavior. The work of agricultura l engineer s has been aggravate d by these circumstances , and this is the main reason why agricultura l engineerin g has relied for a long time on empirica l data. The mechanic s of agricultura l materials , as a scientific discipline , is still being developed at present , and in many cases has no exact method s as yet. However, the method s developed so far can alread y be utilized successfully for designing and optimizing machine s and technologica l processes. The presen t work is the first attemp t to summariz e the calculation methods developed in the main fields of agricultura l mechanics , and to indicat e the materia l laws involved, on the basis of a unified approach , with all relevan t physicomechan ical propertie s taken into account.