Ladies a n d g e n t 1 e m e n , I have the pleasure to welcome you here in Prague in the name of the Czechoslovak Academy of Sciences and to open the Fifth Inter­ national Colloquium on Soil Zoology. We are very glad that Czecho­ slovakia was chosen for this important meeting. It is clear to all of us that the soil plays and will play a de­ cisive part in providing food for the explosive increase of human pop­ ulation. For this reason we watch with great anxiety the negative influence of human activities on the environment accompanied also by the other destructive intervention into the soil ecosystem, its devas­ tation by inefficient management, application of herbicides and pesti­ cides pollution by the waste products of industry and human settlements. The basis for solving these accumulating and now sometimes latent prob­ lems is among others a good knowledge of the role of soil organisms in the cycles of materials and in the energy flow. Soil zoology as a part of soil biology is still at the beginning of this trend The lack of in­ formation about life in soil is obvious when compared with the results of a related biological science dealing with the water ecosystem.