The disposal of municipal sludges is becoming increasingly problematic, because of the greater demand for wastewater clarification combined with increasing sludge volumes which are finally to be disposed of. The dewatering stage involves extremely energy-intensive processes, in which conditioning is unavoidable. A frequent problem in practice is that the operator is under pressure: first, to observe that the required parameters (dry volume of the filter cake, shear resistance etc.) must be guaranteed; and secondly, there is always the problem of reacting to the different sludge states caused by changing feed conditions. Another problem is the diversity of characterisation parameters at each stage of the complex dewatering process. The relationships between the characterisation parameters have been the subject of scientific investigations for a long time, but for the operator of a wastewater treatment plant it is often difficult to retrace the results and employ them suitably. A main reason for this could be the fact that often only information on parts of the whole problem is published, and either only inexact information on the raw sludge conditions or the kinds of characterisation parameters which were used are given. Thus it is often difficult to confirm published results using another sludge system or laboratory method. The paper discusses some important aspects of how to approach the optimisation of sludge conditioning with polymer flocculation agents.