The adaptation of desirable agricultural plants to infertile and problem soils is an increasingly important trategy for improving food supplies in many parts of the world. The plant breeding approach complements, and in some cases may replace agronomic practices such as the use of fertilizers and soil amendments to provide solutions which are economically and environmentally sustainable. The Symposium at which the papers in this volume were presented drew together workers in plant breeding, plant nutrition, physiology, biochemistry and molecular biology to discuss research on gene systems which affect the mineral nutrition of plants. Papers describe successes in plant breeding for problem soils as well as advances in understanding of mechanisms at the whole plant and cellular levels. Papers in the 'molecular' area point the way to the contribution which the new biology will make to this field in the future. The reviews and research papers are grouped under five topics : Better plants for acid soils; Salinity tolerance; Efficiency of uptake and use of macronutrients; Efficiency for iron and micronutrients; Tolerance of heavy metals and boron.