Current knowledge of sewage sludge is reviewed, particular reference being made to the possible effect on the health of herds of cattle. The following measures should be urgently and seriously considered: more effective watching of sewage disposal; assessments on sewage disposals, related to the costs of alternatives; stricter checks on diffuse sources of pollution (refuse dumps, agriculture, etc.); development of long-term views to prevent the appearance of waste matter injurious to health and putting a stop to methods of production in which these wastes are released. The disposal of toxic substances in the environment was reduced by fifty per cent in particular sections during the past five years. When this is chosen as an objective, the Netherlands will be clean in approximately fifty years. In the opinion of experts, this would appear to be a practical approach which can be accomplished by considerable economic efforts. When the thoughtless disposal of toxic substances comes to an end, it will be possible to use sewage sludge in agriculture without this becoming a hazard to the health of animals and man.