Included are papers (in French or English, with summaries in the other language) presented at a UNESCO-International Biological Programme symposium in 1967. The symposium provided an opportunity for the exchange of information on recent advances in soil ecology, with particular emphasis on soil productivity. Papers on broader theoretical aspects and on methodology are presented. The papers are grouped as follows: general problems in soil ecology; structural aspects of soil ecosystems; functional aspects of soil ecosystems; soil respiration; soil ecology in the next decade; and a series of groups dealing with methods of study of particular aspects of soil ecology. These aspects are production by soil microorganisms; macrophytes; the soil mesofauna; arthropods of the macrofauna; root-fluid feeders and nematodes; and earthworms, enchytraeids and molluscs. Bibliographies for each paper and a list of participants are provided. (AL)