In France, areas cultivated with cereals-legumes mixtures have been steadily increasing for 10 years, maibly in organic farming systems. For this management, little advice is available for varietal choice and there is almost no specific varietal selection. Wheat and pea varieties are usually bred under sole crop conditions and farmers base their varietal choice on the traits of cultivars grown in sole crop. However, the performance of varieties in sole crop is not necessarily predictive of their performance in mixture. Based on the study of of three wheat cultivar and three pea cultivar traits in combination, leading to ninety different cultivars inter-specific mixtures, we identified key traits (pea canopy height at the end of flowering and pea flowering duration and, to a lesser extent, wheat tillering ability and pea flowering starting date) that are likely to be good candidates (i) to be taken into account for the success of a mixture, according to the objectives targeted by the farmer (ii) to be introduced as selection criteria in breeding schemes specific to mixtures.