32 field experiments with oats and barley in mixtures and in pure sowing were conducted during 1991-1993, under different soil conditions. The percentage of oats and barley in the sowing blends was 50+50, 65+35 and 35+65. Interspecific competition in oats and barley mixtures depended on soil conditions, sowing date and percentage in the sowing blends. Oats dominated in mixture only under inferior edaphic conditions and by early sowing date, especially at mixture: oats 65% + barley 35%. Barley was characterised by a better ability to dominate in mixtures with oats due to better productive tillering of plants.