The objective of the classification of hazardous chemical substances and commu- nication systems is to provide information pertaining to protection of health and environment.The conference on development (UNCED) in 1992 recommended that the International programme of chemical safety (IFCS) should become the co-or- dinator for the harmonization of classification systems of chemical substances (CG/HCCS). The author presents four systems for the classification of chemical carcinogens (EU, OECD, IARC amd GFR). The classifications differ not only as to numbers but also as to evaluation criteria .The IARC monograph is the most extensive information base for scientists, others interested and legal authorities in different countries. At present it is essential to pay attention in particular to the gradual implementation of EU rules on the classification, packing and labelling of dangerous substances and preparations and to the formation of the OECD programme which pertains to the preparation of a global harmonized integrated classification system. Part of it is also a harmonized system of physical dangers and a harmonized communication system. This approach creates a common and integrated base for the protection of human health and the environment.

        Key words: classification - chemical carcinogens- harmonization