The results of a study of the competing abilities of certain weeds and crop plants are presented. Characteristics studied as possible indicators of competitive efficiency were development of assimilation surface, stomatal number, readiness and uniformity of seed germination and distribution and penetration of root systems.It is shown that success in competition depends on readiness and uniformity of germination under adverse moisture conditions, the ability to develop a large assimilation surface in the early seedling stage, the possession of a large number of stomata and a root system with a large mass of fibre close to the surface but with its main roots penetrating deeply.Cereal crops were classified in the order of competing ability as follows:— barley, rye, wheat and oats, flax.Brassica arvensisandAvena faluawere the most vigorous competitors among the weeds studied.