For the hazard and risk assessment of substances to man and environment several methods are in use in the Netherlands. The methods were developed in the framework of various (inter)national regulations and, consequently, differences occur. It is recognized that unnecessary differences in the models need to be harmonized. The underlying study was performed to harmonize the substance independent parameters. To this end the subject was discussed in a broad group of experts. The report gives the need for harmonization, the followed procedure, the processes within the assessment systems, the parameters under discussion and the harmonized values plus motivation.