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Qualitative and quantitative physical land evaluation methods were developed and linked with a geographical information system (GIS) to evaluate crop growth potential in the European Communities (EC). Evaluation methods comprised expert knowledge and crop growth modelling. The predicted crop growth potential is primarily meant for exploring land use options. In this paper, the wheat crop is used to illustrate the methodology. All potentially suited land units were identified first using computer-captured expert knowledge, followed by calculation of the potential and water-limited yields on these land units with a simulation model. Land unsuited for wheat-growing amounts to up to 55% of the EC area and is mainly concentrated in the Mediterranean countries. Without increasing the EC wheat area, the wheat production volume can still substantially increase by 65% under water-limited and 120% under potential production conditions. Results obtained were used to quantify the impact of set-aside of either highly productive land or marginal land on production reduction. In many EC regions marginal land used for wheat-growing produces at least 50% less than highly productive land. The production potential should be incorporated in set-aside measures to be imposed.